Coming from my experience working in retail, unless the guy had Aryan Nation tats, more likely than not this guy was working in a severely understaffed store.
He was probably in the middle of doing a shitton of time sensitive tasks before he was interrupted by some bullshit manager that told him to help out with the checkout line and then get back to doing the million other things he needed to do before his shift was over.
He was probably doing the bare minimum to be able to say "yes, I helped out the checkout line like you said" before getting back to more important things.
You were never supposed to be able to get to the food court without a membership. Some places care more about it than others but that's the policy.
You entered the exit door to get in. You're supposed to enter from the entrance door and then you can cross over to the food court from there. When you enter always go in through the entrance door that's common sense.
The receipt checkers see literally thousands of people per day and they aren't generally looking at faces they're checking receipts and carts. Expecting them to recognize you out of the hundred people they've checked through in the last 10 minutes is insanity.