There is quite a bit of hypocrisy OP
Can't afford £5 emergency credit for phone
What makes you think the NHS can afford no show appointments?
Didn't want to waste time still going to surgery and not be seen
But it's ok to waste NHS time by not turning up or calling?
Late for appointment
As PP have said, you weren't late. You were a no-show with no contact with the surgery. They had no idea why you didn't show.
Had other important things to do after appointment
The NHS have more important things to do than keep an appointment for a no show and then don't forget the time it takes to write and post letter to said no shows to warn them! It all costs money and time to manage these situations.
I think the problem with this thread OP is that you say you know YABU but then keep defending every single decision you made as if your time and your money is more important than the NHS. Not once have you said 'ok I should have called as soon as I got home' or 'ok yes I can see there is a NEED to have emergency credit on the phone'
The final point I'd like to make - if there genuinely was severe road problems in the area due to closure for an accident and unplanned diversions in place, I'm pretty sure the surgery would have also had other patients caught up in it, or at least have heard about it happening. Therefore it would have been even more likely that they still would have seen DD as they would recognise these are circumstances beyond control, rather than just being 'late', and probably had to shuffle a number of patient appts due to the severe traffic delays.