Hi Brandon!
What happens when that last Persist trigger resolves?
I'd say nothing.
First off, the SHM FAQ says "If a permanent has multiple instances of persist, they'll each trigger separately, but the redundant instances will have no effect. If one instance returns the card to play, the next will do nothing."
Now why should that be so, esp. in light of the fact that FAQs are not always 100% reliable?
The original permanent, let's call it A_0, goes to the graveyard and becomes a new object, A_1, due to the zone change. Now, b/c persist is a triggered ability, it can still see the new object A_1 in the graveyard and can return it to play, where it becomes A_2. That persist can see A_1 in the graveyard is an exception handled in CR 217.1c(2).
Sac-ing the permanent makes A_2 some A_3 in the graveyard.
When the the last persist trigger resolves, it can no longer see "this creature," which would be A_0 (or A_1 in the graveyard) but has become A_3, and hence does nothing.
Did I miss something?
Greetz to Candice and you!