What would you have done if there were money on that wallet? Just curious.
At first, I've had a 'very smart' idea to generate a new address, send them there, then find&contact the owner somehow and pass them the new keys or just transfer to a new account/wallet.. but a quick sanity check proved that finding the owner might be next to impossible. I could put a note on the desk, but then any passer-by could try to claim to be them if I include too many details in the message. I could generate some tx to let them know, but I didn't find any message/text/note on transfers in XMR like here in Hive, bummer. I could somehow embed a message in the amounts (1337 and so on), but heh good luck for them figuring it out. And assumption they still can access that account is pretty weak. Best way to get to them is traceback via garbage locality.. Stick some posters to the doors in 100-150m area. People are lazy, they wouldn't carry furniture to a waste container further away.
Of course, if there was a figure high enough lying there, greed could kick in, finder's keeper's, and so on. I'm still a human not a saint :P But the primary plan was like I said before.
I'm actually very relieved that the account was absolutely fresh and empty. No balance to worry about, no recent sus tx to suspect theft. It's weird to find a private key, but even weirder that it had blank tx history. I actually fully re-synced the wallet two times, and also did that tiny mining mostly to see if the XMR wallet I used really worked and displayed the balance and past txs properly.