You would have found half of it outside the hole. If you tighten them too much they crack in half and the inside goes in the airbox when you remove the screw. The other half has a flange so it would be pretty tough to push that in. The rubber part is all under the fairings. That circular recess is filled with a broad headed cap screw that has a plastic washer under it.
The lowers come loose pretty easy and the two hex head bolts at the back of the fender. The lowers also should have a plastic washer. Use blue LockTite. DO NOT use locktite on the well nut fasteners under any circumstances.
Buy OEM from Partzilla. Or look up the lengths and buy Pro-Bolts aluminum which usually come with plastic washers. PB has well nuts too.
'08 MIDNIGHT SAPPHIRE BLUE Now Deceased