It has happened only once to me and once I remember to a rival in a match. As far as cards I don't really remember.
I think it is worth having 1 reserve GK for these reasons:
1.Peace of Mind during matches
2. Team rotation, you can save 1 or 2 packs by playing your reserve GK in easy matches especially when you are playing in all competitions 2 matches a day almost every day. GK really doesn't have the biggest impact on the match.
3. Recommended players may always be GK if you have only one in the team.
4. He can entertain your players in the bench or dressing room during half time