It does sound like the clutch won't disengage. I would start by checking the clutch master and slave cylinders for leaks. If there is a leak then it needs replaced. There's also the shift linkage to look at. The next place to look would be the throwout bearing and pressure plate, which requires you to take the transmission off. The pressure plate might have bent fingers or the throwout bearing could have been dislodged. At this point you would have the transmission off so could try shifting it directly. The last think to look at if you can't move it by hand is to crack it open and look for a broken shift fork.

Honestly I'm betting on a bad pressure plate. The fingers can bend enough to keep it from disengaging but still feel like it's working. It seems to be pretty rare to break a shift fork and that usually takes a lot of abuse to do.