For arguments sake let's say he HAS been in business for 10 years. And let's assume he's not trying to cheat you.
He asked if you can wait to cash the check and you can say no.
He should have known that he didn't have the money to pay before using the miles.
Like I said, he either has to pay you now, return your miles, or comp you the same miles back into an account with your name.
That's business.