It's my lucky day

I got twenty dollars worth of free gas today! How, you might ask? Well, on the way home from my Dad's house this afternoon I stopped off to get some gas. When I pulled up to the pump, it said "Remove Nozzle. Pump Gas." Hmmmm..that's strange. Usually I have to put my debit card into the machine before it says that. I tried inserting my card. It says "Error". A couple of seconds later it says "Remove Nozzle. Pump Gas." again. I'm thinking at this point maybe you pump the gas before you pay? I know, makes no sense but I didn't know what else to think. SO I started pumping my gas. I had intended to fill the tank, but it stopped pumping at twenty dollars and said "Remove Nozzle." Hmmmmmmm...again. I removed the nozzle, place it back on the pump, and reinserted my debit card. This time it asked me for my zip code. That's what it usually does. So I type it in, remove the nozzle, and pump twenty-three more dollars into my tank. It is at this point that I realize the first time I pumped, something was not right. So I go inside and explain to the attendant that I just pumped twenty dollars worth of gas and I don't think I paid for it(this is the part where my husband is smacking his forehead and saying "You did what?". I can't help it. I am an honest person). The attendant says to me "You are pumping gas right now". "I know, but I just pumped twenty dollars worth and I don't think it charged my credit card." She becomes annoyed with me. Maam(sp?), you are pumping gas right now and when you are done I will be glad to give you a receipt for the amount." First of all, she is annoyed with me? For trying to alert her to a mistake on the gas station's part? Sheesh. Okay, whatever. I and went out to finish pumping my gas. I go back in there
and she gives me a receipt for the last amount. $23.13. I explain to her that I need a receipt for the first transaction, the one for twenty dollars. She looks at me like I have grown two heads and becomes exasperated, explaining once again that she just gave me a receipt for the gas I pumped. At this point I am getting exasperated myself, and there are people in line waiting so I just leave. When I get home I check my bank account and sure enough, they only charged me for the second charged amount. Idiot. But hey, I got free gas.