I asked him where the tooth was, and he said, "It's lost." Apparently the tooth came out at lunch time and fell on the floor. And since he's been told repeatedly that we do not, under any circumstances, pick things up off the floor - he left it there. I'm glad he's following the rules, but sad that I'm not going to have his first lost tooth to keep forever and ever...ew...gross.
The Tooth Fairy left four quarters and two sheets of Wall-E stickers. I hope that's generous enough to appease those who accused me of being a cheap skate. :)