2012 Acura TSX wouldn't start after sitting for 4 days

After sitting in my garage for 4 days while we went on vacation in a different car, my 2012 TSX (61K miles) would not start. The first time I tried, the engine almost caught, but then died. I figured I had just let go of the key too soon and tried again, but all that happened was the starter cranked. I tried jumping the battery, which made no difference (I didn't expect it to since the starter was cranking). I tried several more times, and then on my last desperate attempt before trying to figure out how to work, I cranked the starter for an extended amount of time and it almost caught a couple times before finally sputtering to life.

Does this sound like a bad fuel pump, clogged filter, or worn out starter? I don't know whether the idle days had anything to do with the problem. I have started my car several more times today with no problem. The battery is not quite 2 years old, has a 5 year warranty, and seems to be outputting plenty of power (I seem to have lost my DC volt meter, so I'll get a new one on the way home to check for sure). Has this happened to anyone else?