The Disc-ish disease Uncertainty is easy enough to understand, hinging, somewhat lopsided-ly, on Hiesenberg's Uncertainty Principle, which says that you can either know where a particle is at, or how fast it is moving, but not both at the same time.
Uncertainty can be caught when exposed to a high magical field, such as the Bursar did, while trying to shut off the Thaumic Generator of Unseen University. As a result, he could no longer know where he was, and know who he was at the same time. So, when he was found, and someone said, "Oh, here he is! Bursar, old fellow, what are you doin' on the privy roof without your clothes?" He would remember who he was, and forget where he existed, and disappear, reappearing somewhere else, not knowing who he was again.