Opening it, I saw it was a riddle!
It read:
What dog has legs, but cannot run.
A tail, it cannot wag,
A mouth, but cannot bark,
A nose, but cannot smell?
Before reading the answer, I sat down with my wife and we spent a while pondering the possible answers.
Eventually, curiosity overcame us. We turned over the note to see the answer.
It read: Your dog. I ran it over. I'm really sorry.
I hate riddles.