Probably everyone has had the missing cap at sometime. The cap that plugs the access hole on top of the ft. pass. side strut is always coming unfixed. I've got a simple fix. Run a large straight pin or needle [ a needle or straight pin works good because of the temper and they have a point ] through the bottom of the cap . There is already a notch in the hole on the cover and you can insert the cap and bayonet it [ just turn it 1/8 turn or so ] and the cap is locked in place. If I can get my feeble brain to work , I'll try to load a diagram. I can just barely turn on the computer. Old dog