That moment with Charming, RH and Hook takes place in 3×13, in 3×12 Hook is in NYC for the entire episode until the end when he, Emma, and Henry arrive in SB. Hook escapes the curse, he’s the only one that remembers the whole year in FTL. He knows where to take Emma because he has ALL the memories including SB ones.
I agree, the promo that shows Hook in the hospital is a collection of multiple episodes so in all likelihood this could happen after he brings Emma back to SB. I’m very curious to see how he escapes the WW’s curse to get back to Emma.
I also don’t agree with the whole Hook working for WW or doing anything on her behalf. To believe that means to me that you totally dismiss altogether any character development that took place in 3A and started with his returning to talk the Nevengers to Neverland at the end of season 2. Hook was only ruthless and deceptive in that it served his quest for vengeance which he dropped. To pick up this deceiving nature again implies that this part of his character growth was disingenuous.
I can buy the whole wiped memories thing as far as everyone missing a year. Everyone would know that Regina stopped Pan’s curse and that doing so meant going back to the EF. Since they have found themselves back in SB it would be pretty obvious that something is wrong here (especially if Snow shows up pregnant). If Hook is the only one to have escaped the new curse, he would be the only one to know who the real threat is and the only one who could bring help (Emma) to break the curse and defeat the WW (since he would be the only one other that Emma capable of leaving and reentering Storybrooke).
My only thought as to why the WW would wipe off part of their memories is because she must not have the dagger right away she probably comes into possession of it during 3×16 and thus we get the big showdown and Rumple’s return.