I've never come across this before! has anyone?

Vehicle recovered in, AA told him cambelt has jumped. We fitted new cambelt kit/water pump 3 months ago. First job, checked timing, ok, checked fuel pressure, ok, removed camshaft pully, checked woodruff key(they wear), ok.

Refitted pully & cambelt, traced fault to number 1 cylinder, no compression, removed head, found inlet valve had dropped and was bouncing up and down on top of piston!! and had only worn the guide, had a new guide fitted.

Refitted head all ok.And no sign of the collets!!

John