I wouldn't worry too much, you've done the right thing in putting this out, just set it aside for a week or so to see if anyone claims it, if not then it looks like it's yours, it is quite hard to send to a wrong address unless you are typing it manually so it must be from somewhere maybe you forgot about, perhaps an old faucet?
Nope,Not possible as I remember I generated this address only last month and I have not used any faucets since years ago
So was it sent from this 1LBYV86zufZBXiDTjHiFTM9SGWrfsw9P8k address
Still, if the user is feeling guilty, then it won't be a bad idea to send a signed message to the BTC address from which the coins came. Most probably, it was a reward for gambling / games win. The user might have applied many months back, and he may have forgot about it. I am collecting Bitcoins for the last 5 years, and till now I haven't heard about anyone giving away BTC0.015 without any reason.
This seems the good solution.I will wait for a week and do this