You mean you cannot trust prospective purchasers. It's no surprise that when you have so many vendors insisting on cash buyers who are not in a chain. that you have prospective buyers who don't meet one or more criteria pretending they do.You cannot trust auctioneers.
All the auctioneer can do is ask, they have no means of verifying the answers provided. If you have evidence an auctioneer lied, submit a complaint and they may well lose their license. There is no similar penalty for purchasers or vendors when found out lying.