For reasons I have brought this up is because I am fixing to wright a book called Just Sleep, Just Dream. FNaF story of course. Ok so I looked up What year did the Children go missing in FNaF? I choose Wikipedia of course and I just got an inspiration theory for the missing children. Ok here it is! ENJOY!!!
Ok so, my theory is that when Vincent toke the children, the children saw Vincent as a normal security guard working the day shift. Or as said an employee dressed in a costume. (Another theory that I have is that Vincent was the "Employee" in the costume and lured the children in the back room) My original theory is that when the children saw him and when he killed them, their spirit went into the animatronics and possessed them making them very violent and scary. His face is in their memory and they think that Mike is Vincent and they want revenge from how Vincent killed them and how he stuffed them in the suits of the animatronics. So since they think Mike is Vincent they want to stuff Mike into a suit for revenge.
Ok that was my theory!
BYEEEEE!!!!!