I was driving this car around yesterday quite a bit with no problems,
when I stopped to go into a store for a few minutes.
If you really wanted to try to reproduce it, you could try doing that again. but I would suggest doing it in a safe place, like driving around a parking lot for a whiiilee....
I drove around the corner to where I was going with the e-brake, and
parked it. The car sat for maybe a half an hour. When I came out to
start it and try it again, everything worked fine. I have been trying
to see if I can get them to fail for the last couple days and
everything seems fine.
Sounds like a heat-related issue... or at least affected by it. If it is, then driving it a lot and braking more should cause it to happen again, although I don't recommend you driving it around much at all in this condition.
The brake fluid was at an acceptable level as well.
What color is the fluid? How old?
Could be that the fluid is so old and full of contaminants that when heated, it became very very compressible. although probably not that likely to be or behave THAT bad.
How much braking did you do during that driving around before the problem occurred? Were you braking hard at any point?
How much time lapsed since going into the store and getting out to start to car with everything working again?
How are the pads, rotors, etc.? When was the last time you had them serviced?
How was the fluid level while the problem was occurring?
When did you last change fluids?
If you are feeling gung-ho about it then I would suggest starting by changing fluids; and if you really want to start replacing parts, replace the brake cylinders, unless those parts are relatively new.
If you do not normally work on cars or are not comfortable with working on the brake system, I strongly suggest taking it to a mechanic for proper diagnosis and repair. Brakes are super safety critical for obvious reasons.
ABS system is a good thing to check, as mentioned by someone.
Calipers too, as mentioned by someone, although I feel like it wouldnt be this bad.
it could be anything at this point, you gotta start diagnosis somewhere.
Need moar info.