Are there any physical phenomena that destroy information? Are there physical phenomena, such as wave function collapse or black holes, which irrevocably destroy information about their prior states?
This is one of the current questions of cosmology/physics.  So far all evidence points to the negative inside a black hole so far as quantum numbers go, but it's not clear what you're considering as "prior state."

A simple counter-example is a camera. Once the photons are absorbed by the film or solid-state sensor, all phase information is lost.  Is that what you were looking for?