I felt like I had the bars on my Dirty Disco too low yesterday so, at lunch-time, I decided to move them up.
Previously I'd raised and lowered them without problem but I'd had a new headset fitted since the last time .............
As I undid the bolt on the top there was a "thunk" as something dropped into the steerer tube.
Fishing around, I managed to retrieve a device that consisted of a rubber band around four cylindrical wedges.
This was a new one on me and I couldn't figure out how it worked so I pushed the bike to the LBS for the shake of the head and the sad smile
Five minutes later, I was walking out of there with an intact bike.
The mechanic retrieved another piece (the nut off the end of the plug) from the steerer and it went back together very easily.
They didn't charge me but I'll need to return with biscuits