Replying to Coin Star Question

I work at shaws. so today i go into shaws to buy some gum and when i was buying the gum one of the kids i work with to do him a favor and go cash in this coin star slip he had. so i was like aight since i was waiting for a friend to get his hair cut next door. so when i bring it to the service desk the woman asked me if i worked at the store and i said yes. then she called up the floor manager and said something and i told the guy upfront i was doing it for the kid who was working at the register. so after that i just walked out and he didnt ask me about anything. my question is will they pursue this and investigate what was going on. Like i didnt do anything wrong just was doing a favor for an associate. the problem is that when people cash the slips we have to put an x threw it and obviously this one didnt. will i get in trouble for being a part of it. and if i do can they fire me for that. like i think there is some type of strike thing where u get 3 ur fired. i don't have any/ i usually wouldn't care but i need the money for my laptop and if i lost my job i can kiss a lot of the shit i buy goodbye. any input is appreciated...