I think it is possible he was there as a young boy, but it is a richer story if he was there trying to get Bae. It parallels his current situation trying to get Henry.
The issue I have with Rumple being aware that Bae was in NL is that if Rumple knew that, and was actually in NL to get Bae, there’s no way Rumple would have left without him.
Unless he was forced to leave against his will, but even if so, why was Rumple trying to get to our world, if he knew Bae was in NL? Bae didn’t leave NL until after the Curse was cast.
The only way I could see it working is if PP lied and told Rumple that Bae had been in NL, but had since moved on to the land without magic.
But if Rumple thought that Bae had originally gone to a land without magic when he went down the beanhole, why would he have been seeking him out in other magic lands to begin with?
Doesn’t add up IMO. So I think if Rumple was there for some reason as an adult, he never had any idea that Bae was there.
I also think the doll could have been Bae’s as it didn’t seem big and could have been tucked inside a shirt. If you knew you had to leave behind all you knew, wouldn’t you take something as a memento that was small and easy to cary?
I totally would because I’m excessively sentimental about random objects. But even if so, why would he have had it in his pj pocket when he was taken by the Shadow? He wasn’t anticipating having to leave at that point in time, like he was with the beanhole, so he wouldn’t have had his keepsakes packed for a trip. Unless the Shadow went back for it later, being in Bae’s pj pocket was the only way it could get to NL.