3. The "colloquialism" explanation. Scotty could've been speaking in a figurative manner, saying that his chances of being recovered were so extreme and unlikely that it'd take Kirk coming back alive, reocvering the Enterprise and hunting him down for Scotty to be discovered and recovered.
That would imply some kind of sarcasm or irony in his remark, & Scotty is nothing if not easily interpreted, & everything about the tone, expression & body language of his reaction, points to it being genuine
It seems to me that everyone is dancing around the elephant in the room, or to put it another way the simplist answers is the correct one. Kirk is alive. Or will be, it just has not happened for us yet.
I can't buy that Kirk left the Nexus, prior to the wreck of the Jenolan, & then returned, such that Picard could retrieve him from there, in the 24 century. This, of course, after having been reunited with his comrades like Scotty. Soren seems like a pretty resourceful guy, & he couldn't find a way back in, during that time frame. It took destroying star systems to get him there
There is only two (in universe) explanations
1. Scotty must know that Kirk was trapped in the Nexus, because an investigation into Kirk's death/disappearance was conducted, & they figured out he was in there (perhaps even interviewing people like Guinan & Soren, about their experience there) But there was nothing anyone could do about it, until Picard got him out, & Knowing James Kirk as Scotty does, he probably figured old Jimbo got himself out of there long before mounting a rescue operation to find his lost chief engineer. Essentially, Scotty has faith that nothing could keep Kirk bottled up, in a temporal anomaly, and just assumes he's not in there anymore
2. Highly selective, temporary transporter exposure induced disorientation
I prefer the first theory