All 4 cylinders misfiring after getting gas?

Hi. I hope you have suggestions. I have a 2003 Prius with 212000 miles. I drive about 300 miles a day. I've never had a problem with my car.... Until yesterday. I stopped for gas, pumped, got back into my car and started it..... And horrible knocking noise.... As if I had no oil in it. I immediately shut it off, and checked my oil. Everything was perfect, and oil change just a month prior. There was an advanced auto right next door, so I asked them to run diagnostics, which they did and showed that all 4 cylinders were misfiring. I spoke to a local mechanic, and he said he was sure it was the gas. The guy at advanced assured me that the gas station has the best gas around, oddly really pushing that it can't be the gas. I had the repair shop tow it. Within a half hour the mechanic called and said he siphoned the gas and no water and it smelled good. He also told me it wouldn't start. So I had it towed from Clewiston to fort Myers for $250 to a Toyota dealership. After doing a half hour diagnostic they call and tell me I need a new hybrid battery!!! My battery was at full charge, I have always gotten 42 mpg consistently, and have always ran full charge (less the top indicator line). There was no warning lights of any kind that it was failing. I always keep my screen on energy.... To make sure battery always working. When she called from Toyota, she said they also had to charge the 12v... That the hybrid battery must've killed it.... What am I an idiot?! She said its probably because the car day so long.... When is the last you even drove this car?!... She asked! I said well 300 miles on Tuesday and another 40 yesterday to the had pump, which is where it stopped. I really don't think my hybrid battery just went.... Could it be a computer thing causing it to throw this code? Could it be I just need a new 12v?... Though that one is only 6 months old. Any thoughts? They and $3200 for the battery. I think they've lost their mind. Also, she refused to let me speak to my service tech. Thanks for your help people. Just very frustrating, Beth