The following rec'd from a resident of San Juan Capistrano:
Mission S J C has Fr. SERRA Chapel. I'll bet this is what you are thinking of. The only remaining building in Ca. where Fr. SERRA said mass. SERRA is open daily & on the tour. SERRA Chapel can ONLY be used by the old local families for services. You are correct because this is an old adobe. Ghosts are in SERRA Chapel. So you were right. S J C has a SERRA Adobe which is lived in. HA!