Worked in retail (Germany) for a while and I have seen a couple every day. 500€ bills were rare though. And our registers where technically not allowed to accept more then 999,99€ in cash.
One time a customer payed a pack of gums with a 500€ bill. It was legit, so started counting to give back the 499,11€. As I was about to start to count a second time to verify, she just grabbed the money and stormed out… it was odd, I was 70% sure that I didn’t count right the first time, looked outside but she was gone. When I had to count the money after my shift I had 100€ too much. My manager was as confused as I was and I have never heard anything of it again. Weird one.
Nice to know, that I possibly won’t run out of learning material then :D