Yeah, it's pathetic alright. When I was a kid, my grandmother used to send a few dollars cash in my Christmas card. I really hit the big time when she upped it to a $5 bill. Nowadays my out-of-state relatives send checks for us to buy the kids presents and we take pictures and make sure the kids know who it's from.
It's never a good idea to send cash in the mail, but this time of year people let their guard down sometimes. Your mail thieves were probably looking for cash and checks. PO Box or post office drop off... good ideas.