Lyng17 said, "who knows what others are going through?". I am well aware that events currently happening in my own life almost certainly affected my frame of mind that day. However, that is my problem not the sales assistant's and is no excuse for my tetchiness.
Had it been a local shop, I would indeed go in the next time I'm passing, buy some insoles or some other small thing and apologise for my terseness on my last visit. But I have now left the area I was visiting so that will not be possible.
Witzend, twenty years ago I did some volunteering with an organisation which ran training sessions in libraries for people wanting to acquire basic IT skills. In my early 50s at the time, I was well impressed with the number of people in their 70s, 80s and 90s who turned up, eager to get to grips with 21st century life. In the main, they were quick and avid learners and some went on to more advanced courses in word processing, use of spreadsheets, databases and so on. Many were learning so they could communicate more easily with distant friends and relations; others because they saw the potential use of IT skills as an aid in their own volunteer activities, others because they were simply interested. Yes, there was the occasional creator of a forgettable password but they fell into all age groups!
I was quite shocked at the number of much younger people who arrived at these sessions - late teens and early 20s - who had no real interest in learning but felt they had to be able to tick the 'IT Skills' box for job applications. It did make me wonder what had been going on in schools in the 1990s that they hadn't learned these basic skills and had their young imaginations fired by all that potential opening up in front of them - but that's another subject.
Katek, you are probably correct that my comment was just as ageist as the other woman's! I daresay nobody here will believe it now but I think I'm generally a fairly nice person and not much given to public displays of bad temper. Unfortunately, it was not a good day and I let myself get riled by an unintended slight.
Many thanks to those who have supported me. I DO think it's important that everyone takes a deep breath and pauses for thought before generalising.
All over 65s are not technophobes; all politicians are not lying sleazeballs; all teenagers are not drug-addled muggers; all those using a wheelchair are not deaf, blind and mute ("does he take sugar?") etc and so on.