I think this is unprecendented with Steam. I have heard of games being delisted but I can't recall Valve ever removing them from peoples' libraries.
If I owned a copy of this game on Steam I'd be requesting a refund immediately; they have been known to make exceptions to the standard 2-hours rule under special circumstances.
Also, Steam has a game files backup feature, it might be a good idea to use that and wait for someone to figure out how to disable Steam DRM