A coworker of mine had a destination wedding and no one from work was invited (obviously) but because he is a good friend, on our last day of work before he left, I gave him an envelope of congrats. I think he was embarrassed or something because he quickly said thank you and put it in his work bag. In the card was a cheque that has yet to be deposited. This was over a month ago.

Do I let it go and just wait for him to find this? Do I let him know what was in the card?