2004 Toyota Corolla - Sudden loss of clutch engagement

I was driving to work this morning when all of the sudden at 30mph the
clutch disengaged.  I had just shifted in to 3rd when it happened and initially
i thought i hadn't got it in gear properly, but I tried several times and several
different gears and none of them would engage the transmission.  The
clutch pedal did not feel squishy or odd, and as far as I can tell it's the same
as it's ever been.

My first inclination is to think the clutch itself has gone out, but the
suddenness of the issue seems very strange to me.  I have not felt it slipping
even once.  Hydraulic issues also seem unlikely as the pedal feels okay.  I'm
able to put it in any gear just fine, but when i release the pedal nothing
happens.  I had to get a ride quickly and get to work so I didn't have time to
investigate it any further.

Any ideas on what could cause something like this would be greatly
appreciated. Thanks!