Some of my best sessions were after doing a good deed for a provider. Grabbing some bags and pitching in would have been a good way to warm up.
If I already knew the provider, it might have been different.
If it wasn't already 20+ minutes past my appointment time, and if I had all the time in the world, it might have been different.
This lady knew she had a 9 am appt and decided that wasn't very important and decided to go shopping instead. Or, if she didn't know, then there's something seriously amiss with their scheduling procedures.
As it was, she had one chance to make a good first impression, and blew it.
I don't know too many places where, if a monger showed up 20+ minutes late, he would still be accommodated. I've read plenty of reviews where the monger was turned away for being late.
I can appreciate your good nature about these things, but I make it a point not to be late and expect the same in return. Who's to know whether she didn't have a 10 am scheduled, or a 10 am walk-in were to show up, in which case I would also have gotten short-timed, another of my major pet peeves with some AMPs.
An emergency would be a different matter, but grocery shopping is not an emergency.