Property manager writes large check to owner without documentation

We have a board member that had paid a rather large bill for clean up of our common area out of his pocket and had our property manager cut him a check back. The invoice was hand written from him to our property manger.When asked for back up the only thing he supplied was a invoice from a company not related to this kind of work, a few months after the fact,typed and not dated or signed to him.The company in question is owned by a friend of his and not incorporated. We asked him for a copy of his check to the company and or if paid in cash a withdrawal slip from his account and proof of a deposit on that date into the other companies account.Nothing has been produced and our board won't push the issue. Any ideas on how to proceed. We are talking about a large sum of money in the thousands.Something stinks.