Actually hungryhippo I don't think that 'shit happens' is the right approach. The best response is 'how can we work together to help DS learn to take responsibility for his learning?'. It might mean that you put up a checklist near where his bag is for what he needs to have packed each day. Making sure he has the required items that he needs for his homework. In the classroom, it may mean a star each day he remembers his homework, which leads to a reward at the end of the week if he brings it everyday that week. A checklist next to his school bag reminding him of what he needs to unpack. (These are all things I do for my own DS, as well as for numerous children in my classroom - they are still learning, and still need support from parents and teachers).
He is only 11 years old, and whilst it is very important that children learn to take manage themselves, he's not going to be able to flick a switch and suddenly be Mr Responsible. He needs to be scaffolded and guided to help him make the right decisions, and the adults in his life need to help him with that. Any 11 year old is going to look at his iPad, and look at his homework and decide to play on the iPad. He's not going to automatically know that one is more important than the other, because right now, it's not, at least in his own mind. Eleven year olds aren't going to have the capacity to look at their school bag and know exactly which items they need to include, they need a guide. Sure, some children might, but some need a lot more support before they 'get it'.
It's better for a teacher to ring the parent early on and say 'hey, Bobby didn't bring his homework today, is he doing ok with it at home or is he finding it challenging? What can we put in place to help him?' rather than letting it go for months before flagging it up.
I don't think the teacher was professional in making a comment (we have a 'hang it up six times before you open your mouth' policy in my team), but I think that's a separate issue to the one of the child not turning in his homework.