The first sign got taken down around the time there was the whole drama about the BLM giving some of SKyline to the tribe--they also took down the Bighorn sign at that time. It seemed evident they were anxious to offload Skyline and maybe removing the signage was part of saying 'this trail has nothing to do with us anymore?" Just my guess.
I agree that the failure to note the snow and ice issue is puzzling as that causes at least as many rescues. Still something is better than nothing.