Wilbur Friske Theory *spoilers*

[Roy595]

Spider Guy cuts off his tongue sometime before you arrive as a result of it swelling because he'd eaten so many of the spiders. I think the simple fact that the Spider Guy was missing his tongue, and the note mentions Frisk dragged in a man who had no tongue, says that it was Spider Guy. It can't be a coincidence as it expressly mentions the body missing a tongue. Besides, I dont remember hearing anything about dogs burrowing through the walls (the creature that gets Spider Guy makes distinct dog-like noises) AND it did mention Frisk wandering off into the mines and he did burrow through walls. It had to be Frisk that got him.

Besides, there were people still alive in the Shelter when you get there, so it isn't too much of a stretch to believe that the whole ordeal occurred between Phillip's arrival and his exploration of the Kennel.

It just makes sense.