Only in a "ribbon for participation" context does this make any sense, a context to which I do not subscribe.
Saying their actions bear no fruit this time doesn't and IMO shouldn't discourage trying again next time.
I'd agree it
shouldn't but it's a matter of psychology. If you want to encourage behavior, you reward the behavior. If you want to discourage a behavior, you punish it.
Participation Trophies work, but there's a bit more to it than reducing it to participation trophies.
If they try to open a door and for whatever reason cannot, so be it. They'll likely never know if they were "supposed" to get past it or not; and if they're that keen on getting through they'll go back to town and load up on some more resources that'll be more likely to succeed.
A party is more likely to just ignore a door they aren't supposed to open. And if they ignore it, what was the point of putting it there in the first place? It'll also confuse the players, because they'll think your descriptions are less interactive and more narrative. There's a door there, but is really a door or is it another stage-set?
The core of exploration is to see what's there, even if it's nothing.
Nobody really likes to look at nothing, though. It's boring and it wastes time on describing the nothing rather than actually playing the game.
Yeah, that's 'ribbon for participating' again.
The reward for checking all the rooms can be as simple as not feeling later like they might have missed something. And-or not having to go back later to finish off threats they missed the first time through; I've seen this several times both as DM and player.
Gaining something for searching a room isn't necessarily giving them a participation trophy because they won't know they didn't truly earn it. You don't tell a child they'll get sweets everytime they play, you tell them they get sweets everytime they play well. That not only reinforces that they got the sweets of their own power, despite you planning on giving them the sweets regardless, it gives you power to go back on the idea of rewarding
everything since it was never an agreed upon condition anyways.
It's not like they can re-search a room over and over to find infinite gold, you tell them they didn't earn it. Likewise, if they roll so pathetically low because they had the guy with terrible perception search, they don't find anything because they didn't earn it, even if the criteria for earning it was hardly an inconvenience.
When I design a typical dungeon-based adventure I put in the treasure in full expectation that about 1/2 of it will be found for sure*, about 1/4 of it might be found if they search, and the other 1/4 will be found only if they're very diligent and-or rather lucky.
I structure my dungeons fairly similarly. Despite my constant rewards, players tend to miss 1-2 treasure hoards in a dungeon because they either forgot to inspect something or they didn't think about it.
Personally I prefer it if now and then they come to dread rolling initiative, as it means they'll (in theory!) look for ways of accomplishing their goals that involve things other than just sheer brute force.
By dread, I don't mean fear. It's perfectly fine if a player hears your description of a crimson dragon opening it's maw and preparing to unleash a shower of flames. That's awesome. It's not awesome when players hear you say roll initiative for the group of mooks and the players audibly groan and bang their head on the table while a player turns on the shredder preparing to recycle the leftover of their characters.
That said, though they're probably going to win their combats most of the time (even though it might not appear so at first) and thus earn the reward of both the win and the xp that go with it, by no means does that say or imply they're going to hit on every swing nor does it say that an individual PC won't die or have some other major Bad Thing happen to it.
Most attacks from a balanced fight are designed to hit based on the bounded accuracy. AC doesn't get all that high even at high levels while to-hit goes into the +11's to +13's. It's rare to come up against an enemy whose AC drops your hit percent below 55%. Spells almost always do some form of damage as a guarantee. Even if the enemy succeeds against the save, the caster will get to roll their damage dice.
In comparison with that exploration is (usually) much lower-risk, with the trade-off being the tangible rewards - be they treasure, information, whatever - are less frequent.
Of course, exploration needn't be low risk-low reward. Traps up the ante for collecting treasure. It makes it very tense when the party finds an obviously booby-trapped cache where they must find the mechanism, disarm it, then grab the treasure without activating the trap. And it won't feel like they merely participated since they did have to make hard decisions and perform difficult tasks to acquire what they earned, and with a risk of damage or worse.
