teach the kid a business lesson and keep the money. he's accentuating the fact that there was no verbiage "non-refundable," neither there was a "refundable." Seems, he did not mention any extreme reasons for the money, he was not very communicative after giving the deposit, and simply changed his minds.

and dont be afraid of legal proceedings. most likely, it will not happen. even if it will, the common sense is on your side.