That customer sounds like an idiot. I worked as a checkout operator many years ago and it annoyed me when people licked notes to hand to me and this was long before covid. There's no need anyway as you can easily separate bank notes, I sometimes think they did it to flash the cash. No one's impressed.Sounds like I would get on well with your mum haha
A work colleague of mine tells the customers in a loud voice that she is going to go get some gloves because you have just licked your fingers
Sadly one customer rang up our boss and complained about her saying this to them .... She got dragged upstairs and told to be more polite...... Unbelievable even if covid wasn't around us staff shouldn't have to touch another person's spit when handling cash.
There's something really crappy about taking the time to call in a complaint about one member of staff - unless they'd been really horrible or did something obviously wrong. Sounds like one of those customers who thinks all supermarket staff are there to be talked down. I hate that attitude.
Anyway, getting off my soap box now!