OK I’ve been sculpting perfectly this past 2 days on my HD subdivided mesh, then today i tried to switch HD off to start sculpting and polypainting elsewhere, then suddenly when i press “A” key the HD geometry dissapears, but i mean its hidden or erased, i dont know what but i cant see the part i was working on, then zbrush crashes and closes.
the Geometry HD tab dissapears whenever im working on that subtool, instead it looks like regulary subdivided, but i can’t work on the rest of the piece, only on the “HD” area.
what should i do, i can’t finish my work . and the deadline is closer and closer 
please heeelp