Not sure about the disappearance of his tip-up, but I’m willing to bet he’s overstating the distance he was from it. Not calling the poster a liar, just that most people are very poor judges of distances in that range! Kinda like the guys that tell you they shot their deer at 400 yards….most times that is the human eyes exaggeration and not even close to reality.
Nonetheless, Protourbaits, did you see anyone in the vicinity of the tipup while you were out there? You posted this on the St. Croix forum so I am assuming that is where you were fishing? I’ve had tipups tangle into a nasty mess while fishing the upper Croix, is it possible your line got twisted or caught up with something floating down-stream and somehow got pulled down the hole. 