I talked to the the mechanic today and he said the clutch pedal engagement point needed adjustment. The way it was before the adjustment, the clutch wasn't fully engaging. As far as I know I was able to shift smoothly and without any grinding noises until the problem happened. The clutch is in good condition though, it engages well and there's no slipping. The master and slave cylinders were fine, clutch fluid was full and clean, no leaks anywhere. I told him about the possibility of the clutch line being close to the exhaust and the fluid boiling, but he doesn't think that's the problem for two reasons. One, the clutch line has a heat shield and it's far enough away where it's probably not affected. Second, the fluid was in good condition, if it overheated and boiled it would be broken down which wasn't the case. Their recommendation is to drive it for now and see if the problem reappears. If it does, he said it's probably the clutch needing replacement. This part didn't make sense to me since he said it's not slipping and the engagement is good. I'm gonna drive it for now and see if it happens again. I'd happy to hear what you guys think. BTW, the clutch is the original one and has 42K miles on it.