Good for you, but depending on where they got/saw your address, someone might be trying to launder it...and they may not be able to receive it back at the original address it was sent from, anyway.
Hold onto it until someone contacts you, I would say. Don't try to cash it out. That way if law enforcement sees it and gets ahold of you, you can provide them with contact details from whoever is looking for it. It certainly sounds suspicious and like someone is trying to take advantage of your goodwill somehow to launder it.
Jeez, didn't see your response. Now i'm confused! I guess I will just wait until somebody contacts me....
That's what I would do. Now that you've mentioned you have that amount of BTC, be very cautious about scammers trying to get it out of you or claiming it's theirs when it's not. Careful! If no one contacts you after a few weeks, then IMO, you're safe to do what you please with it. Good luck.