^we're the opposite. . .
DH's family is hardcore about thank you's, I on the other hand wasn't raised to write them but I do!
I always write them, well, always TRY to write them! But I've never let anyone wonder if I got the gift or not:nogood
I'm the same way, I wasn't raised to write thank you's but DH's mom writes them for EVERYTHING. I have a great stack of Thomas Kinkade cards to use for anything that comes along and I enjoy sending them because most people don't and I like getting mail so why wouldn't someone else?
But the reason I said what I did the first time was because if you are giving an unrequited gift to someone, you should just let it blow in the breeze because they didn't tell you to give them a gift, you did it on your own. If you hold yourself to the standard of responding with a thank you no matter what, that's fab because it's a nice gesture, but not everyone was raised to think the same way (that's a whole other thread). The bottom line is that gift giving should be a selfless act, you shouldn't expect a thank you or it just turns the situation into making you feel good for what you've done. You know you gave a great gift, leave it at that.
If I give things to someone, or do a favor, or anything along those lines, I don't expect a formal thank you or repayment to stroke my ego, I do it to bring joy into other people's lives however I can.
May I ask how old the boy is? If this situation were in my family, my mom would have at least made me call to say thank you (since when I was younger the internet wasn't so huge and most family members didn't know what email was anyway). She should be at least giving him the tools to be polite and well-mannered for later in life, or he may end up a boor without realizing it!