I've done a lot of online sales with a fair amount on eBay but mostly chestnuts through my web site. Fortunately, all of my eBay buyers have been happy. Every once in a while I get some negative feedback on my web site and I try to be gracious about it, though it can be challenging when some comments come out very silly (one buyer once complained that there were water spots on the chestnuts, LOL). It seems when you handle things in a courteous manner such as you did, things usually work out well.
The only thing I would suggest differently is that you explain which plant in the auction photos is the one being sold. I think it is pretty obvious which one is a plant in a gallon pot but the larger plant with fruit might be what a buyer remembers when placing their bids.