Ah, yes, the old "this is my rack and nobody else gets to share it with me" parking style.

If you have an old but functional bike and a good lock then overlock you bike to the rack around tha( one and put a note on your bike with a cell phone number stating that if your bike needs to be moved then please call as it is your primary transportation.

I had sympathy for the part time employee until I saw how he parked.

If the store owner has contact info then see if you can get that to contact them yourself, if not then maybe have your info forewarded to the bike owner. Or ask when their work hours are and try to catch up with them at work.