i did something totally petty at work

so i work at this mall clothing store and one of my coworkers named liz is always giving me crap about how i’m better at customer service than her. like yeah we all know that but im not gonna brag about it or anything. anyway last week she was supposed to cover the cash register while i took a lunch break and she said no because she was busy with something else, so i had to take her shift. omg i felt so bad because i knew it was my day off technically but also like… liz deserved to be punished for not being there when she said she would be. so as soon as i got back from lunch and took over the register, i decided to do something super petty in revenge. i grabbed a bunch of pens from our supply drawer and hid them all around the store. under products, behind mirrors, inside drawers… basically made it impossible for her to find anything when she was supposed to use the cash register. and you should have seen the look on her face when she started looking everywhere for pens and stuff, thinking something was wrong with everything in here. i kinda felt bad about it afterwards but i couldn’t help laughing inside too because honestly… if she had just done what she said she would do there wouldn’t be a problem. plus now everyone’s talking behind her back saying liz is always screwing up and making more work for the rest of us, which is pretty much true anyway so its not like i’m completely out to lunch here. lol but still, hiding all those pens… that was petty and childish of me. am i really the asshole? i feel bad about it now but also kinda good too because liz needs to learn to be a better coworker.