My own headcanon right now (most likely debunked tonight but just in case it’s not) is that Zelena imprisoned Neal in a mirror just before he was able to save Rumple and the next curse was cast. He is able to travel between them, and watch over Emma and the rest of her family, but unable to comunicate. He can occasionally escape, just as Ozma could in return to Oz, but not for long and he can’t reveal his true identity.
*whimper*
However, I do like it. Now that you went through and found all those, there are a TON of mirrors in the first 2 episodes.
It also would be a parallel to Charming being trapped in the mirror in Season 1.
NICE!
Edit: And I just thought to myself, what if this is the price of some sort of magic he tried to use to get to them?
Maybe in 315 he find a book of spells or something that can get him back to Emma/Henry but the price for trying it is that he is sucked into a mirror and can only see them that way