TO the OP, you made an effort, that is all you can do. Donating what you found is a very kind gesture.
When I DJed at parties and clubs, several times after the event I saw rolled up currency lying around in the venue. However, I had no interest in touching anything that was likely in at least one persons nose and likely still have traces of cocaine or other drugs on it
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The most I ever "found" was by in my radio and party DJ days. I was unofficially guest DJing at a club (the club DJs would sometimes stop by the radio station I was on at the time and gave me an open invitation to come by). While in the booth the club owner stopped in to see how things were going, with 2 women with figures that would make a grown man cry. He hung out for about 20 minute, on a couch in the booth with the women, watching me mix records, before moving on to another one of his businesses (this one happened to be a "gentlemans club"). about 30 seconds after they left I took a break, and noticed a roll of bills next to the couch. The club DJs said oh crap, that's probably his. I volunteered (as the guest) to try to track him down, so I ran out thru the club outside.
He was still in his car with the women, so I knocked on the window. I showed him the roll, he reached into a pocket and got a look that I knew he had dropped it. He wanted to "reward" me by inviting me to hang out a the "gentleman's club", and one of the women made the comment along the lines of "I could have a lot of fun with an honest man". But... that just was not me, I graciously declined. He left it as "come by anytime, its on the house", but I never followed up.
Yeas ago of my brothers and a couple of friends were once cutting through a lot in a sketchy neighborhood at dusk when they noticed a backpack in the brush, they looked and saw it had money in it... but they figured this might be part of some illicit transaction, so they just ran off as quickly as they could.