HR question for those with experience

I recently started a new job at a small manufacturing company. Since they're small, they have no HR department, so at least some of those duties fall to me, even though my background is accounting/finance.

We had a guy that was a temp worker for several months on a contract. He did a good job, so the company hired him full-time not long before I started there. Everything was fine for the first month, but he got a couple of advances on his paycheck that we just deducted out when it was time to pay him.

However, 3 days into the last pay period, the guy disappeared. His boss and a few others have left messages for him, no response, nothing. So, he had three days pay coming, and he's the only person in the company that doesn't do direct deposit. He has an actual physical check in the office sitting there waiting for him.

Oh, it also turns out he borrowed $500 from his boss right before he disappeared, too. Nothing in writing - just, one of those handshake deals. (We even had a person call some local hospitals, etc... nothing.)

I assume that we would need to mail the check out to him. I'm also assuming that the guy's boss has no recourse, since nothing was put in writing.

Are my assumptions correct, or not?

Thanks