I don't wait for people. Gladly setup a time for them to come and get a product, but I always tell them that the first person with the $ that shows up gets it and to please call before coming to make sure the item is still available. No different than an item on the rack at walmart sellling out before you get there even though you saw it online and it said they had them in the inventory.
$ talks.....everything else walks.......as they say.
Does suck though. Put a down payment on an item so they wouldn't sell it and had a written paper for the down payment and they still sold it that day while I was at work. Than tried to keep my down payment. Hence the requirment for the paperwork when any $ is exchanged.