Someone tried to scam me at my local gas station today

Someone tried to scam me at my local gas station today As the title suggests, someone tried to rip me off at a gas station today and I’m pretty mad about the whole incident. Okay, so let me explain what happened. I was low on gas so I pulled up to my local gas station. I had 50 dollars on me at the time which I plan to use it all on purchasing gas. When I got to the front window, I handed the cashier my 50 dollars. I made sure beforehand that it was the right amount. Then I headed back to my station and put gas in my car. Here things got weird. On the pump display, it said I only got 20$ worth of gas, not the 50$ that I paid for. Strange.. so I went back and told the cashier what happened and he claimed that I only gave him 20 dollars. I was confused at first because I knew that I’ve given him way more than that. I did my best to tell him that he’s wrong and that I actually gave him 50 and not 20 dollars that he claimed. He kept on telling me that he only received 20 and then he showed me 2 10 dollar bills. When In fact I handed him 3 10 dollar bills and 1 20 dollar bill. He must’ve hid the other bills. Keep in mind I am a severe stutterer. When I confronted him about it, I was stuttering so badly that the best I could do was to repeat the same two lines that I could think of at the time to make it seem like I’m the one who’s telling the truth and to make it sound at least somewhat convincing to the others who were waiting behind me. Since there were other people behind me waiting for their turn, after nearly 2 minutes of me stalling the others and myself repeatedly stuttering and trying to say stuff like “you’re ripping me off” and “can I please have my 30 dollars back”, the cashier just gave up and he put the other 30$ of gas at my pump station. So yeah sorry, i just wanted to vent and let it off my chest. Thanks for reading