I’m inclined to believe that Regina stole it because at some point Rumple shows up at the Charmings to tell them that Regina is planning to strike back against MM. (it was sneak peak #3) so I think it happens before sneak peak #5 where Charming and Rumple find the bag. Charming guilts Rumple into helping because Rumple owes a debt to MM and then they go off to the heart vault to find the bag.
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"He was a lot of things to me" "The only conclusion was love"