OK, so by Emmet not going to the movie and hooking up with Edna, And then when Marty and Doc go back, Doc disappears while they're in the car. When Marty arrives in the alternate 1985, my question is, if that doc didn't exist, and the new one never invented the time machine, hence all the things they changed in 1955 never happened, meaning Doc never built the time machine, then why didn't the time machine disappear as well? Also, why didn't Marty disappear as well? I mean, in BTTF2 they explained that while time changed, since they were in the time machine, the time stream changed around them, but then wouldn't Doc not disappear?? Just seems like a loop hole. Unless Doc did build a time machine in secret without Edna knowing. But even then, if the events in 1955 were never changed, and the time machine was never built then it would also effect the changes made in 1885 and 1931. Unless someone wants to explain this to me. But I don't think Doc Should have disappeared.