Simple? math question... Aug 9, 08, 4:45 p.m.

So my father in law asked me this question, and I have no idea the explanation:

3 guys decide to split the cost of a $30 hotel room, so they each throw in $10.
After they pay and go to the room, it sucks, so one guy goes down and asked for some money back. He gets $5 back. He can't easily split $5 three ways, so he gives them each back $1 (including himself) and the other $2 to the bell boy. So each guy paid $9 essentially.
3 x $9 = 27
$27 + $2 = $29
What happened to the other dollar?
Am I missing something here?