What if the event that caused Lina to disappear is also the cosmic inspiration to Marvin for rebirthing

I.e. whatever happened to Lina in the windmill that made her permanently inaccessible was just the same thing that happens to kids being rebirthed? Could Marvin have seen that happen and adopted his method from that?

That might could offer an explanation for why she isn't around and thought dead after that, but pops back in later when it's super important... She didn't literally disappear, she was permanently altered by what happened, i.e. Lina left the room. I guess the windmill disappearing in this idea would be dependant on the "other angle" theory.