Nope, more commonplace. The expression is from old times, the reason you might visit a church (and neighbouring acreage) still happens today and will never cease.
Or maybe they rang a bell just before they put you in the ground to make sure you were dead. If you woke up and escaped the coffiny doom, then you'd have been saved by the bell.
It is indeed very plausible and you're so close I'll give you that.
We're looking at the time of the plague, when coma's were difficult things to diagnose! Some people would fall in to a coma only to awake two or three days later - although they would appear dead to the world. They would be left for a couple of days to see if they did come round at all. Anyone wondered why we had funeral wakes??
If the person hadn't awoken after the wake period they would be buried with a string around their wrists which was connected to a bell above ground - hence 'saved by the bell'. Of course, someone would have to listen out for any bells ringing and check that they weren't being swayed by the wind, so often someone would patrol the graveyard at night. it wasn't a pleasant time to be up and about so the expression 'graveyard shift' was born.
Anyway, after all that cardinal richelieu has the next honours.
