This is an update to my previous post. Son #1's teacher did indeed receive my email and got the three boys together to sort it all out. Here's the official story: A (the boy who claimed the money) is in the English as a Second Language program. When Son #1 asked A, "Did you lose this money?" A said he thought Son #1 was offering him the money (as in, do you want this money?). So naturally he said yes.
The teacher gave H (who actually lost the money) $10 from his own wallet. A now sees the misunderstanding and was to bring the money to the teacher today. The teacher sent Son #1 home with my money - I didn't have the heart to make Son #1 drain his piggy bank. He also emailed me a nice note about how impressed he was with Son #1's integrity.
So now I hope everyone is happy. Except perhap A who must have thought he was attending the friendliest school ever.
All's well that ends well.
[I let Son #1 keep the $10.]