One of my memories was losing track of where my mum was when we went shopping. She was right behind me, but 5-6 year old me panicked and ran out of the main doors.
There was a school trip to teach us personal safety issues (not sure the age, I'm going to say 11 with low confidence), and one of the tasks was (to the entire group) "Go along this corridor to meet the policeman, Officer FooBar"; we went along the corridor, someone not in uniform asked us where we were going, one of the group said "to meet Officer FooBar", and this un-uniformed person said "I'm Officer FooBar, wait in this room". Then he left and the real Officer FooBar came in and asked us to explain the situation, and that we'd been fooled because we'd volunteered too much information. (The fake Officer FooBar was also an officer, but one who was pretending to be a Bad Man™ who was pretending to be an officer).
The UK school system, at the time I went through it, the year before you finished you were sent to a "trident work experience" thing for a week (I think to keep them out of the way of those doing exams) — mine was to be a teaching assistant in a primary school. The kids all called me "Mrs Ben" because to them "Mrs" was the title given to all teachers and they didn't get the difference between family names and given names.
https://en.wikipedia.org/wiki/List_of_Georgia_area_codes
Of course, they're increasingly meaningless now that everyone has cell phones and gets to pick an area code.
OK, technically my parent's number was 10 digits rather than 5 because it was <areacode>577099, but that didn't matter as I'd almost always be local to that code, and if not could state my home town if talking to an adult who was doing the calling (or if I'd dialled the operator number, which I'd need to do anyway for a revere-charges call) and they'd know that bit.
I grew up memorizing my dad's number and was told to go find a trusted adult, stranger danger, etc. There was only one time I needed to use it, and I recalled it perfectly fine. If your kid has trouble memorizing it then turn it into a song, give the letter version, or change numbers. It worked fine then and works fine now. Get a grip.
Cant imagine growing up under that kind of parental surveillance.