Happy birthday, etc etc.
Chances are he might not make it over hear. But there's always the remote possibility that a friend of his will say, "oh, saw you gotta lot of happy birthday wishes on IMDB.com." That forum is well known in the industry.
Just wanted to let the guy know, "was thinking about you," even by strangers. Everybody likes to be told happy birthday, well maybe not on your 30th or 40th.