My family just threw a bridal shower for FI and I. My aunt and uncle gave us cash instead of an actual gift. We opened the card, saw the cash and put it back in the card and envelope. Well, when we got home the money was missing. There were other people helping us get all the gifts into the car, and it's unclear whether the money was lost or stolen (I hate to think it was stolen).
What do we write in the thank-you note? I read before that you shouldn't thank people for gifts you never got the chance to use, but we do know exactly how much money went missing and who it was from. Should we explain what happened or just thank them and not mention it?