anemone disappeared

hi guys.ive had my Rbta for a year.was the centrepiece of my 5ft tank. always beautifully thriving to 4x original size.. but 5 days ago in a space of 2hrs moved into a cave and disappeared.can barely seat but its very deflated. tried to give a little shrimp . no grab as usual no stickiness.water...

It is a 26 gal bowfront with lots of live rock but this guy was big. Here last night ... gone this morning. My clean up crew is one cleaner, two peppermints, 5 hermits, one turbo, one emerald, and a variety of tiny critters that scurry around the rock. The white guy quickly found a spot in...