I had just compiled my map to test in TF2, when I got an error because I had forgotten to split up a concave brush. After rebooting Hammer (it tends to stop working after running TF2, going in to sleep mode, or just sitting there for a long time), it prompted me to remove the invalid geometry. I clicked yes and resumed working in an area with only brushwork. Only later did I realize that all the (non-brush) entities were gone (after I had already saved the map). View->Hide Items is not checked. I (foolishly) don't have any recent backups, one autosave is from after the incident, and the other 4 are from two months ago when I first started the map, for some reason. Does this happen often, and is allowing Hammer to remove invalid geometry a bad idea in general? Any chance the entities are still somewhere in the map, just hidden away somewhere? I know this is my fault for not for not making backups, but Hammer is getting good at finding new ways to anger me. Edit: I just searched through the map files, no mention of the missing entities (besides now-broken I/O), guess they really are gone.