Long story short:
I borrowed my cousin's A4 (2007, with 36000 km on it), to go look for my keys that I'd lost the day before. I spent five hours driving everywhere, looking for them. Around midnight, I gave up, and wanted to take a break so I picked up a couple of friends, to grab some tea and relax for an hour or so. One of the friends I picked up asked me if he could drive the car. I was tired, and I have a hard time saying "no" to close friends, so I let him.
Halfway to our destination, he decided to stretch the legs a little, not peeling out, but just nearing redline per gearshift. I let him do it because I was too tired to actually speak to anyone at the time, and was too pissed off about the keys. Shifting from first to second he was fine, second to third, he did some sort of misshift. We didn't hear anything, but he started panicking and I sort of woke up from my daze and told him to calm down and not panic, and just change gears like a human being. He tried to shift it from third to fourth, and after the car got out of third, it wouldn't go into fourth, from neutral. The clutch pedal was also stuck to the floor.
I knew right at that point that this was going to be bad.
Now my friend doesn't realise that it's his fault, and is probably not going to pay for it, I cannot tell my cousin that some stranger (to him) was driving his car and ruined it, so I'm footing the bill.
I'm an idiot.