i was following a tutorial to ad wetness with ultra dynamic weather and my gpu failed and ever since a bunch of random materials were deleted and and now anytime i try to drag a new mesh in that meshs materials get deleted.
If the materials are still there, but showing blank, could be the shader cache.
Try deleting the shader cache and it should rebuild next time you reload the project (warning might take a while depending how many projects and materials etc etc.)
Worth a try!