Are you saying that your players know that treasure found is generated by their search tests, that it exists or doesn't exist based on what they roll? Is this really how you play? It's one thing for this to be a true yet hidden aspect of the game, but another thing to be an open fact. I want to think I'm misunderstanding you because if this is how you run these things, then why do your players bother coming to game? If adventure treasures are simply generated by their own dice rolls, then were is the sense of a real world existing behind their adventuring? It would be like playing games of Bethesda's Daggerfalls where all dungeons and awards are randomly generated. I must be misunderstanding you.
Edit: Unless, perhaps, these little rewards are so ancillary and unimportant to your players that it's just not that big a deal. That would be an unusual circumstance, but within the realm of possibility I suppose.
2nd edit: I actually found the liquid on the floor idea to be very creative, and I also would have rewarded it. Just because something has been thought of before, doesn't mean that everyone has been informed of that thought. There is nothing new under the sun, as King Solomon writes in Ecclesiastes. It doesn't follow then, that there is no creativity under the sun.
Yes, my players know my rules. I dont tend to hide house tules from them.
As for your seeming disbelief, are you aware that what I described is how Foraging checks in 5e are handled? Gm assigns a DC based on the situation and terrain and a successful check finds useful/valuable stuff and failures can get really interesting. The GM did not need to pre-game "place" flora, fauna and water for the players to find. The results of checks determine it. Iirc its DMG under wilderness stuff but mentioned in the DMG.
Also, perhaps you have heard of Random encounters where other rolls adjusted by situation, actions, choices etc can lead to various events that the characters may encounter. Agsin, not needed for the GM to pre-set these to specific spots.
There are also AP where it defines miscellaneous "stuff of value kinds of things that are scavengable etc - determined randomly, not by pre-set location and amounts.
The perhaps significant difference between my point about it and the poster I responded to was his was given automatically as a reward for creativity. It did not "exist" was not true for him either until X happened. The difference was in theirs X was "gm liked what the player said" and for me it was "a success at a task by the character" if you will.
As for why my players bother coming to game, if I go by what they have told me, it's because they love my games. I don't think this house rule had any real impact on that, negatively at least. For the guys with exceptional search skills (and less often others) it does often lead yo very meaningful scenes and follow-ups, so I can say it added to their enjoyment in a few cases just off my head.
Are these finds unimportant to the characters, not hardly. To the players, nope. Heck, some of them have been more important to them than the "placed" treasures were.
As for your take on creativity, that's great. I am all happy for you 9n that regard. But, curious if you would call it "creative" the next three times, the next ten. If not, if that water trick stops generating treasure cuz it's now labelled "routine" , seems like it will stop getting used.
In my game, once it's used, once its seen as "effective" it will keep its benefit long term. That way we can maintain a very consistent world. If something stops being effective, they look for "why" and z better "why" than "it's not creative snymore."
But that's us.
Not necessarily for everyone.
Oh, edit to add
At the start of each session, my players deal me cards face down
I take them and use them to add to the evdning's play.
Hearts equals chance to help someone with aid or get aid yourself.
Diamonds means opportunity fore more loot.
Spades equals challenge OS an environmental or passive passive nature - floods, bad weather, blighted area.
Clubs represents additional combat threats.
Sometimes, these radically change the defining in unpredicted ways.
So there is another case where we get results from more than just GM predos.
That has been loads of fun, according to them.