kermitt

Was on a track day and running very well all day until all of a sudden engine started drawing in masses of air and started cutting out as I pulled into the pits and would not start again.

After getting a tow home the guy driving it managed to get it to start but have since noticed that my idle speed adjustment screw is missing from the inlet manifold after finding an oil spring tucked away at the back of the head. The area around where the screw goes is a bit oily too.

Question is what would have caused the screw to come undone like that and if I can get a replacement what can I do to stop it happening again?

Car is only mildy tuned (say 160bhp ish) running chip and exhaust???