Why not do a text message that is very nice, but simple such as "H, Happy Birthday! I hope you have a nice day!" and leave it at that. No mushy stuff, etc. There are no expectations of a response and who knows, he just might text back...but keep your expectations low.
Coly, your h hasn't forgotten you. How could he? You've been together for a while and the memories that you shared are in his heart, soul and mind. He may give the impression that he's forgotten you, but he hasn't. Let me give you an example. My xh left in December 1999 and I met up w/him in November 2005, the day after Thanksgiving. He mentioned that he thought I would be out doing holiday shopping since that's what I use to do when he was w/me. I said no, I do my shopping now at different times. See? They do not forget.
Hang in there. I know it's tough not hearing from him...but you will when he's ready.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.