was i wrong for this?

Yesterday I bought a pack of gum from Eckerds and the cashier was talking to an old lady in front of me about how rude people were. I was at the end of the line. when it was my turn to pay, I noticed the cashier had one arm. So I pay for my gum, get my change and am standing there waiting for my receipt and she balls it up and throws it in the trash. She didn’t give me the option to have the receipt. I am paranoid enough with people racially profiling in stores and switching purses that I feel the need to verify my purchases. So I ask her to get my receipt, thinking it wouldn’t be a big deal. After like a minute of searching, a long line materializes and all eyes are burning a hole in the side of my head for making the one armed lady hunt through the trash for a receipt for some gum. Then she gets this attitude and puts the trash can on the counter and asks me if I want to look for it.
how did it get to this?

“Nah, ‘s ok.”
and I leave.