A few months ago, the hubby and I saw a resale car we wanted. We put a small cash deposit down. Then the seller received a higher offer after accepting ours and refused to sell. Yes, we could have forced him to sell but with so many deals floating around, we figured 'why bother?'
So we asked for the deposit back. The seller stalled for months. The hubby kept calling and calling. Whenever we were in the area, we'd drop by the seller's house (where the original transaction took place). We were a nuisance but we got our money back.
(Ironically, the new buyer's financing fell through and the car remains unsold. We, since then, paid all cash for a better valued vehicle.)
I know you don't want to be a pain in the butt but if someone owes you money and you want that money back, the only way you'll get it is to ask and ask and ask again. If you don't want to chase after your money, the solution is simple… don't loan it out or otherwise do business.
If this is an at arm's length transaction (i.e. you don't really know the borrower), you should follow the proper collection procedures.