<prompt> Human: Hi there folks, sorry if this isnt the right place for this, I didnt find much help on google. So I bought an item at a seasonal Halloween store and paid 12 dollars, Im not feeling too well so I hand her the 50 I have, take my change and leave. I went to use the 20 I had left and it wasnt there, so I check my receipt, and sure enough, she put in 20 dollars... Im really poor so this is a significant loss. My question for you fine folks is how in the world do I prove that I paid with a 50? Thank you! PS: sorry if Im a bit rambly, Im suuuper tired.  <response>: Go back to the store and ask. In my experience, 50 bills are not that usual for people to be carrying around since 20 bills are more common in ATMs, so maybe its still in the register wherever they put them. That also is a plausible explanation for why the clerk may have made this mistake. Talk to manager. You cant prove your assertion, but you wont get anything if you dont go back to discuss it. 