Why...didn't you just leave? Once they announced they were calling the cops you could have just...walked out? If they want to be that stupid you really don't have to play along.

I've been on both ends of this kind of scenario (as a cashier and a customer) and I never encountered any problems. I really don't see why someone would get so up in arms about it. It happens, and there's really no harm done.

This is the excuse thieves give who use the technique of grabbing a bunch of random stuff to hide what they were stealing. They also use this excuse when they get caught. I'm a cashier and I hear this excuse a lot. It sucks, because normal people actually do forget their wallet, but we aren't mind readers. If what you're trying to buy are expensive, small, or commonly stolen items, it looks suspicious.

we are missing some basic information here what country and what area are you in it just feels like there's country cultural some basic country cultural information and we don't have

I had the same situation happen to me yesterday. I just put the items in the bag I was also buying (you have to buy your plastic bag here too), when the person in-front of me was finished paying I told the cashier to hold on to that and I'll be back in 5min. It was all fine - I came back and picked up my groceries