Mr. Smith gave the Hotel Clerk $15 for his room for the night. The Hotel Clerk discovered that he had overcharged by $5. The Hotel Clerk sent a Bellboy with 5 one-dollar bills back to Mr. Smith's room. The dishonest Bellboy gave only $3 back to Mr. Smith and kept the extra $2. Mr. Smith has now paid $12 for the room and the Bellboy has $2. Since $12 plus $2 amounts to $14 (not $15), what happened to the extra dollar?