Subaru Clutch Repair Question

Hoping to get some feedback though there is not much I can do at this point. I just completed a 4,200 mile roadtrip (98% highway) with my 2009 Outback Sport. In anticipation of the trip I brought my car to a dealership to get everything checked out / repaired. $2K later I have new brakes, timing belt, water pump, gaskets, etc... I told the mechanic the clutch pedal was starting to feel sloppy and they did a full check of the clutch system stating nothing was wrong.

Throughout the trip the clutch pedal felt looser and looser. The only times I shifted was at gas stations or rest stops, so not very often. With 200 miles left on my trip the clutch pedal loses all pressure, gets stuck to the floor, and I have to limp home in 3rd gear. A quick check reveals that the clutch hydraulic cylinder is leaking, no big deal. I drop the car off at the dealership upon my return.

I get a call from the dealership today and the entire clutch is toast. The same dealership that informed me three weeks ago that not a single thing was wrong with the clutch. Is it common for the clutch to go from 'nothing wrong' to 'needing complete replacement' in such short time? Or did the mechanic miss a potentially avoidable $1,600 problem?