Yes, I'm sure, it was a "bill", "legislation", he signed it with a real pen too.
Do a google.com search, type in "President Bush, stem cell research, signature, signs, bill"...there are several articles, read away...
Which bill was there that he signed other than what he stated he authorized? It looks as if to me its still sitting in the Senate where Republican Senators like Hatch and Specter support it...