I made this theory awhile ago, and put it onto a discussion, but thought I'd put it here too.
The background facts:
1. We know Purple/Phone Guy dies in the 1st game
2. Purple/Phone Guy does not use in-game mechanics (all the animatronics 'killed' him at once)
3. The souls of the children (and possibly their bodies) inhabit the 'original four' animatronics and the Puppet
1. When Purple/Phone Guy figured out he was going to die, he attempted to escape (and succeeded) via the right door, bypassing Chica and/or Freddy, and heads to the East Hall Corner, Dining Area and Restrooms (CAM 4B --> CAM 4A --> Opposite side from CAM 1B --> CAM 7) before eventually reaching the safe room (next to the restrooms, behind the camera). This assumes that again, in-game logic was correct and the animatronics came the way they do in the game, but they could all have come from the left. Or right.
2. The animatronics reset to their positions (Show Stage/Pirate Cove)
3. Over several (or one) night, what happens in the minigames in between nights in FNaF 3 occur (Purple/Phone Guy with the help of Purple Freddy lead and destroy them, freeing the souls). This also explains the absence of the original animatronics in the third game.
4. As Purple/Phone Guy hides out in the safe room, the 5 children appear (the one you control being the Puppet's spirit) ambush him. Purple/Phone Guy panics and runs into Springtrap. NOTE: I know that Purple/Phone Guy knows the danger of getting into Springtrap, but he panicked.
5. The rest is history, he laughs and dies.
6. (Very unlikely) He leaves you the Night 5 message. NOTE: We do not know for sure when the message was recorded. DO NOT IMMEDIATELY ASSUME THE NIGHT 5 MESSAGE WAS RECORDED AFTER NIGHT 4.
That's my theory. Feedback?
NOTE: Thanks to Centaura for the map which I used. I've edited it to show Phone/Purple guy's path.