Let This Be a Lesson to Me

I have a little story about something that happened to me recently. I'm going to make a long story short, and try not to be overcome with rage as I type. As you may have heard, I am an artist. As many creative and thrifty people do, sometimes I trade goods/services in exchange for other goods/services. In this instance of trading I face painted for quite a few special events at a local restaurant. In exchange for the face painting I received credit, a "tab", from this (not so fine) establishment. Well, the last event was January 10th, and as I was leaving I chatted with the owner, telling him it had been a good experience, clarifying that this was the last event, and that we were on the same page as far as the status of my credit- I still had some outstanding. SOOOO, fast forward to last night when I stop by the (not so fine) establishment. My father was in town for the evening, and I wanted to take him out for dinner, so we headed there. It all was lovely until the time came to settle the check, which should have gone like this: get the check, write down the total in my planner where I keep a tally, give it back to be comped, and leave a tip for the usually pleasant service. Not so much. Upon getting the check the server informed me they weren't going to comp my check. It wasn't her issue, so I asked who told her to say that and then confronted him. By the way, I don't even know what gave him the authority to make this decision; he's not one of the owners and hasn't been a part of the arrangement. He told me they were "done with me" and aren't doing my tab anymore because the face painting gig is over, and then gave me the run around when I demanded an explanation. I asked him to call the owner, and he didn't. I left a note for the owner, asking for explanation but haven't heard back. Basically, I just got treated like a piece of crap AND ripped off for the work I did. OH, and on top of that it kind ruined the nice evening I was spending visiting with my father.
Today and then this evening I hoped I 'd hear something from one of the owners; I want to think they'd try to make things right. We'll see. At this point in the evening I'm done thinking about it, but it's not over. I intend to get a full apology and compensation; it's just ridiculous that I will likely have to fight for something that is rightfully mine. I held up my end of the deal. The lesson in this for me is: no more verbal only trade agreements. From now on it's details in writing.