Also a car one...sorry for the length, its ridiculous.
Tyres needed replacing, so already expensive. Couldn't find the locking wheel nut. Had only had the car just under a year so wasn't 100% sure we'd been given it. Called the garage we got it from. Had the car/house/loft upside down looking for it (had recently done a massive sort out so it could have been anywhere). Still couldn't find it. Had a long journey to make and MOT due, really needed it done ASAP. Two local garages tried and failed. Local dealer could book us in for 6 weeks or order a replacement in two weeks, which may or may not work. All expensive and none in the time frame we needed.
One of the school Mums husbands is a mechanic and offered to weld them off. It took him forever but he managed it, but the car developed a weird problem with the alarm - it just wouldn't stop going off. Had to unlock and then let it lock itself. Needed to be sorted, but got tyres changed and went on the trip.
Got the car into the dealership to investigate the problem as local mechanic couldn't fix it. Took weeks. Had to hire another car for holiday as the courtesy car wasn't big enough. Total cost approx £2.5k.
BTW, there is a technique to disconnecting the battery on some cars (for safety you disconnected the battery when welding), which wasn't done and caused the alarm problem.
Last week, over a year after the ordeal was over, I found the locking wheel nut.