I thought this too. Cora seems so powerful. When Regina told Rumple that Cora is alive in FTL, Rumple look worried. Also there was no need for Cora to tell Rumple that she could restore memory. Because if there is one thing I’ve noticed about her; is she is a very selfish woman and only does things for her own benefit.
But I’m surprised that Rumple seemed to take her word for it and trust her so quickly. Because she is a very unstrustworthy person, and if anyone should know that it’s Rumple.