Add.: another poster suggested that someone had a bit of a laugh with you by saying it, which is also entirely possible. Basic joke.
I believe them. Cash machines dispense(d) them, but usually only if you withdraw 1000DKK or more in a single transaction. That's unusual for people that rarely use cash.
I had them as I was following the official advice to keep some cash around in case the banking system is hacked etc, but I spent them and withdrew 100DKK notes when the advice was updated to point out that if everyone had only 500DKKs at home it wasn't very flexible.
I am slightly ashamed to realise that my banking app shows I haven't made a cash withdrawal in Denmark for more than 12 months — the second part of the official advice is to use cash occasionally to keep that system working.
See also: https://www.bbc.com/news/business-48993008
which as well as explaining the background to the note and debates over whether it should be taken out of circulation also points out the context the average British adult was making about 20 cash transactions a month as of 2018 (none of them involving £50 notes)
They are effectively becoming the new $20 with inflation continuing upwards, and I expect their popularity to continue to increase.
Let me introduce you to a $2 note.
Your best bet of happening into a $50 is if you go to a bank for an in-person withdraw and they ask you for preferred denominations. Generally the money is dispensed in $20s even there unless specified.
Your second best bet would be if you're selling something "on the side" and the purchaser uses a $50 in a transaction, which I would say is also rare these days, most people use Venmo or equiv.
Your best bet of handling a $50 is probably as a bartender, or of course as a bank teller.
I have held $50s a few times in my life, and even my reaction is "huh, a $50, don't see those often"
A friend's dad showed me one when I was at school - that's it. He seemed amused I hadn't seen one before, then after making a minor show of it, as if it was some precious, rare item, said he'd never previously seen one either. They've been uncommon my whole life, and apparently could/can be difficult to actually use, shop assistants being unfamiliar with them and not confident in their legitimacy.
I expect today most people would use bank transfers for the sort of sum where the sheer number of notes would make a £50 one useful.
But when the bill is £45, there's no problem anyway.
(Maybe they're a bit easier to get hold of now, especially with recent inflation? But I don't use cash as much as I did when I was younger.)
I felt like I was very cool considering how rare they are.
I have had many places reject $100 bills though.
I’m that weirdo that tries to pay cash for most everything, so sample size is large and across a diverse set of businesses.
Due to what I tend to pay cash for these days (lunches, drinks with a friend, etc.) and prices being what they are, they are rapidly becoming my “go-to” denomination.