Do TOFS Key Bosses Despawn

[Tiltjag]

So I've been trying to get the key from the 4th floor off and on for a few days. Tonight I get Amontehepna to pop on the opposite end of the floor and kill him. As expected I see Cara Omica on track. As a druid it takes me a fair amount of time to clear the mobs and med up so I can move forward. About halfway to the coffin room Cara disappears from track. Do the key bosses despawn after a certain period of time after being triggered?