Out of interest were the plugs also changed during the service 1000 miles ago?

Any lack of compression on a compression test? Assuming the hook has left the chamber it may have collided with the valve or seat on the way out.

Regularly serviced with all correct oils and only serviced 1000 miles before it developed an issue. Plugs were changed about 9000 miles previous.

Thought I’d reach out you guys since I’m getting nowhere.

My Astra VXR stalled early December, then misfired a bit and was then ok for a bit. It started misfiring again but only under hard acceleration. Codes came back as cylinder 3 misfire. Ordered a new coil pack but didn’t fit it. Took it for its MOT and passed fine, no misfire. Driving it home and the engine started ticking. Rocker cover off, plugs out. Plug for 3 had dropped the electrode hook into the piston so it had been sparking onto the plug thread. Anyway. Replaced all 16 lifters and it had a new cambelt kit from Courtney. Still ticking. Went to garage, they thought it was the bottom end but on removing the sump the crank and big ends are fine. Visible signs of metal in the oil. Camera down cylinder 3 shows 2 small witness marks from where the piston had hit the bit of spark plug but no sign of the bit. No deformity on the crown and no scoring on the bore that could see.

Any ideas?