According to... who?
I'd say it's a better wager that they found a way to regain their memories similar to how they did it in Storybrooke. Both Regina and Gold were adamant
that they'd all forget about Storybrooke once the curse washed over them. Saying they didn't lose their memories at all is just talking straight out of your ass.
Only Emma and Henry were given false memories.
Which is probably why the method used for the others didn't affect them; they were under a completely different spell/curse.