Thought I would add some feedback as to my recent experience.
Had rMBP about 2 months. All was fine until last week.
Mine has now done the same as OPs. Out of nowhere I got a white pixel on the left upper side, looks about 4x4 in pixel size. At first I thought it was dust but it felt like a grain of sand which came away as i moved my finger over it, leaving just the white dot and what looks like a hole in the outer screen coating. the dead pixel is easily noticeable with it being about 4x4 in size.
edit: --- Its just happened again on the right side near the center whilst watching a movie. same description - felt like a grain of sand as if a pixel has popped or something and left its residue on the screen!
So now I have 2 dead 4x4 sized pixels and 5 tiny 1x1 sized ones. This is on an LG screen with IR too.
Taking it into apple on Saturday this is totally crazy!!