the cop does not have the authority to ban OP from any store but...
I suspect the OP misunderstood the wally world employee though as walmart tends to issue company wide bans.
OP didn't ask about the charge itself but IF OP is honest, I would defend myself if I was in her place. In fact, just recently I almost did a similar thing. Purchased a half dozen or so items. Three were quite small. I actually checked to make sure they wouldn;'t fit through the holes in the bottom of the cart before I placed them there. When checking out, apparently a couple slid towards the back and when I looked into the cart, the butt flap was horizontal and apparently blocked the view.
as I was checking out, the cashier placed my bag o' stuff into the cart and saw one (and ONLY one of the items). She thought maybe another shopper had left it in the cart so she asked me if t was mine to verify. I said yes, I intended on purchasing that item but stated it was with a couple other small items as well. Lo and behold, I had placed one on the register counter but missed the other two but the cashier saw one of those two but missed the other after looking directly into the cart.
So, what the OP described can happen. Don't know if it did happen the way she stated but it is believable.

