I just realised that. Was he ever available in gen 3 or was he like Arceus and never actually able to be captured.
There were specific areas that looked like they'd be event triggers for Jirachi, but the only ways to get him were through the Colosseum promo disc or the European/ Australian versions of Pokemon Channel until gen 4. Unless, of course, you lived in Japan, then there was a Jirachi event almost every year.
EDIT: Forgot to mention that Jirachi didn't have a gen 5 event outside of Japan either.