mixture screw fell off inside airbox

[a1quattro]

hi trying to get my 1984 2ltr coupe gt running , after recently giving her a full service including new fuel pump and filter ,cam belt water pump .Had played with mixture screw before all this work carried out , to get her threw mot , TODAY I couldn't seem to get 3mm allen key to do anything , so have just removed metering head lid off airbox only to find the mixture screw sat in bottom of airbox . . I spent 2hrs trying to wiggle it into postion onto end of allen key but I just cant seem to get it to screw back into bottom of metering head , very very fiddley , any suggestions