So sorry for your loss, Notarehearsal. I am glad you got some comfort from his friends. It makes a lot of difference to know he was loved and valued by other people too, and that even though he was only around for a short time, he made his mark.
I lost my brother when he was 17, and I have also lost contact with his friends. I would love to be able to talk to them about him.
When someone dies, Lights, you feel you have to hang on to their memory through loyalty, and sometimes that makes it difficult to move on. It's early days for you, but maybe you could write down for yourself everything you can remember about this person, both good and bad. It might help you to get your thoughts in order and also to address any guilt you might feel - about not being in contact or anything else.
Also, writing about it might be useful so that your memories are uppermost in your mind when you talk to their mother, just in case she wants to hear you speak about her child (like Notarehearsal). Maybe at some point she might want to read what you have written, too.
Look after yourself too. Don't underestimate the effect this will have on you. Time changes things, and I hope you will eventually be able to move on.