You just reminded me of mine, at about the same age.
I'd been getting around on an Enfield racer for a year or two and loved it. I'd even saved up paper round money and upgraded the back wheel to an alloy one, with a racing cassette on! I was taken to stay with my grandparents down in Devon for a couple of weeks and the wheels had been taken off, and the rear derailleur loosened, to fit the bike in the car boot. So on the first day there I put it back together, and used my grandad's long handled ratchet to tighten everything up, including the tiny bolt that did something between the derailleur and the derailleur hanger. And watched as it fell apart like a piece of plasticine. Still, should be okay...
Went out for a ride round the block, which included a decently steep hill, so I got out of the saddle and powered up it, to hear an awful noise come from the back of the bike as it ground to a halt. So the plasticine bolt was there to stop the derailleur from falling into the spokes, and this is exactly what it did without the bolt.
I took the back wheel to a repair shop who said it was beyond help. Can't remember what happened next, but seem to recall riding out to my uncle's farm at some point during the holiday (to help build a swimming pool, have a couple of pints with the men at the end of the day, then vomit moussaka all over the kitchen sink after drinking too much on an empty stomach, but that's a different sort of twonkiness altogether) so maybe my grandparents shelled out for a new back wheel for me, bless them
Sadly, my mechanical sympathy has not improved with age and I still scuttle off to the LBS or garage whenever any vehicle needs fettling.