It is unknown who cause the bite of 87' but in this I guilty Vigo the Snake!
1. He appears only in TRTF 3, so he been putten away from people and visitors! (Also invistigators)
2. Phone Dude& Guy don't often talk about him, maybe becouse of bite of 87'?
3. When he jumpscares you he opens his mouse and results a bite!
(Kidna short xD!)