use the database that contains the stored proc
then substitute the name of the proc where I have procname:
sp_helptext procname
Or if you have the Sybase Central admin tool in place, just browse to the proc, & right click.
There is a setting that can hide all proc text, "select on syscomments.txt" and it is unlikely you have set it. And a stored proc that can hide text permanently, again unlikely that it has been invoked.