Brainstorming about Observation checks

Someone over at the Warhammer Forums was having a problem with Observation checks for clue-hunting in a published scenario. A PC searched a location that had a hidden object, and the adventure called for an Observation check vs 3 Purple dice. The PC failed the roll, and suddenly the rest of the party wanted to dog-pile on it... despite there being no in-character reason for the PCs to suddenly find that particular bookcase interesting. Success rates in Warhammer are generally high, so 3 or 4 players all making the same roll is pretty much a guaranteed eventual success no matter the difficulty.

That GM wanted advice or options, and I gave them 12 possibilities. Cross-posted here:

1. Only allow one check per location or clue, ever. Let the PC with the best Observation check roll it, and all others in the room add white dice for assisting. If they ask to check there again, explain that the consequence of failure was that their characters are now convinced there's nothing there. Just like how failing a Charm roll might actually upset the NPC you wanted to charm. Or like how failing an attack roll means the foe gets to counterattack before your next action.  Or how a failed Athletics check leaves you at the bottom of a ravine with several wounds. Failed checks have meaningful consequences.
2. Only allow one check per day or per act. This is the less extreme version of the above method. You're temporarily convinced there's nothing there,  but you can come back later with a fresh perspective after thinking about it for a while.
3. Allow additional attempts on the spot, but make each subsequent roll have escalating difficulty.  Ever have that experience of looking for your lost keys and you search the same room again and again only to eventually find it in plain sight somewhere you just could not think to look at? So frustrating, right? You can simulate that by adding +1 purple per check that preceded it. Eventually the banes and chaos stars will start to look daunting.
4. Allow the rolls, but award Stress and/or Party Tension for each one after the first. "I all ready looked over there, Johann, I'm tellin' you it's not there!"
5. Make each subsequent search take longer, or make more noise. Eventually an NPC will hear them or walk in on them. Can be combined with methods #3 or #4.  These are great bane and chaos star consequences, for example.
6. Make your rolls per room instead of per sub-location within the room. The scenario says there's a 3-die test for checking the shelves. Don't roll when they check the shelves, roll when they check the room in general. Difficulty is 4 dice if they don't go into detail, reduced to 3 dice (or even 3 purple plus 1 white) if they specifically mention the shelf. EDIT for context: The original forum post had this extra complication that the scenario notes called for a roll only if the PCs examined the shelves.  I originally didn't mention it here, as it's mostly beside the point.
7. Use the die roll only if the PCs search the room but fail to mention the specific part of the room the clue is in. If they specifically check the shelf, they automatically find the thing that's hidden there. If they just toss the room, they roll the 3-dice.
8. Reduce all search difficulties everywhere to some standard number you're okay with, probably 1 or 2 purple. Use that same difficulty whether the hidden thing is plot-critical, trivial, or completely nonexistent. It's a bonus to the GM in that the PCs can't metagame the difficulties, but also a bonus to the PCs in that the hardest difficulties have been reduced. Everybody wins.
9. Make all searches have a difficulty of exactly 1 purple, but with a variable (hidden) number of successes needed to reveal the clue. Similar to the mechanics the game uses for First Aid checks, and the recovery rolls from Diseases/Insanities/Criticals. The 1 purple is so there's a chance of stress or location-specific consequences. If the scenario notes call for a 3-difficulty die roll, translate that to mean they need a net of 3 successes to actually find the clue. Tell the players that this is the way you're handling it from now on, but never tell them the actual number of successes needed to find a specific clue in a specific place.
10. Base the difficulties on who hid it, not how well they hid it. An NPC who's very careful and secretive sets a 3 or 4 die search die difficulty on his bedroom and office even if there's nothing there. Let the PCs know that's how it's going to work. They still get metagamy info, but it's more about the personality of the NPC instead of revealing "the clue is on this shelf somewhere". It's worth noting that "NPC is private and detail-oriented" does not mean "NPC is hiding an evil secret" but either could result in high purples on the search.
11. Take the approach that the Gumshoe RPGs use: Clues are meant to be discovered, they exist to advance the plot. Make clue discovery automatic if the player's search the right places. No rolls at all. Fast and simple, and it favors the players so most of them won't complain. One small problem is that Intelligence and Observation are slightly devalued this way, so it might not be an ideal method if a PC has invested heavily in those stats. (As those with low Int + Obs will steal scenes that would otherwise be his spotlight moments.)
12. Make clue discovery automatic so the plot doesn't stall out, but still roll the normal number of dice just for the bane & chaos-star results. If you technically failed the roll, you still get the clues, but it means you've left evidence of your tampering that the villain will later notice. This keeps the plot from stalling out (which can often happen if the PCs miss a vital clue) but it still rewards players for investing in Intelligence and Observation. 

To that, I could have easily added a 13th option: "Ditch those players and find yourself some new players that can keep out-of-character knowledge compartmentalized for the sake of the game." I decided to keep that one off the forums, since it's a little incendiary.

Personally, I've been using method #1 in my campaign. Reflecting on it this morning, I'm now inclined to use methods #9 and/or #12 in conjunction with it.