I'm sorry it has turned out like this for you but I don't think the school is 100% to blame.
Communications are a two-way process and as the author, you are the one with the most responsibility.
You may feel that you have done all you could, but it was clearly not effective. It should have worked, but similarly buses should run on time, and there should be no crime. It's idealistic and far from realistic.
If your child is in a school with 1300 pupils and 200 staff members, then communication is always going to be a challenge. Imagine if you were in a business environment with this number of people!
I know that schools always give you the line that the form tutor is the first line of contact blah blah blah, but it doesn't take long to realise that this isn't effective, especially when there is a time element involved.
Put yourself in the shoes of the form tutor and the games master and try to imagine what it is like to make sure they are doing their best for all their pupils (your child not being their only one). It's not easy in a large school. The form teacher is in teaching for his love of his subject, not for his admin skills. There is very little flexibility of time to do admin tasks in schools, because everyone has to conform to the timetable.
As for the games teacher - your DS shows up in his games kit and plays football. What is he to do? Abandon his class to go to telephone you? Imagine that it was about another child - would you have been happy that your child had been abandoned?
Seriously, if you want such individual attention, you have to send your child to a smaller school where everyone knows everyone.