damn managers

One of the managers is a really big flirt with all the servers/bartenders, except me of course. So this ex-server who always comes into the bar always flirts with him and stuff. She never pays for her drinks, or at least never full price. I don't know how much she pays though (if at all) because I've never served her. So she orders two shots from me, right where the manager is (cuz she's flirting with him). I make her the two shots, she throws down a $10 bill, and turns away before I can stop her. The total should have been $14. The manager SEES the $10 bill. He didn't stop her and ask her to put down more money. So I assume (yes, making an ass out of myself) that he condoned that the drinks were on the house and that the $10 was tip. Of course, I probably should have asked him, but being the dumbass I am, I didn't. So I just put the $10 in the tip jar. Then he comes over and yells at me and asked why I didn't charge her for the drinks. It was busy so I didn't have time to explain, but I said that she gave me $10 and I assumed that was tip. He just gave me a mean look and took the $10 from the jar and put it in the cash register, aka leaving me with zero tip. First of all she was an ex-server and she always leaves a lot of tip, so my reasoning wasn't completely off the wall. Secondly, she always gets free drinks from the managers so I assumed this was the case again, since this whole thing happened RIGHT in front of the manager -- it's not like I'm blatantly trying to steal money from the bar RIGHT in front of his eyes!

The next day I come into work, the head manager confronts me about this. I explain to him my situation and he lectures me about giving drinks away and blah blah, then he says he doesn't want me handling money for the rest of the night and wants me to do the service bar. First of all the other 2 bartenders can't handle the crowd and they are definitely not good enough at multitasking (aka serving drinks AND clearing the bar, since we have no barbacks). Secondly, the customers know me and they order drinks from me whether I am serving or not. Thirdly, the servers don't tip us out for making drinks for them, which is the policy here at the bar, so fuck that. Anyway, to make a long story short, I get completely pissed off but instead of expressing it, I decide to be more patient and talk with the manager again and explain my situation more clearly. Whatever, him and the other manager probably don't trust me, but it's because their management sucks and it's not my fault they're greedy little bitches trying to pin the blame on me and make me look like the bad guy. Look, if he REALLY cared about the money he could have stopped the girl and made her pay the right price for it. But obviously he didn't care about it enough to make himself look like a bad guy in front of her, so he wanted ME to be the bad guy, and wanted me to take the blame for it. Zzzzzz. Again, what can you do.