That old thread you saw could very well have been mine! I didn't discover that mine was missing until I noticed that my trunk was getting excessively dusty from driving on gravel roads. That never happened to my Gen 1. So I became suspicious, and through this awesome group, discovered the issue and the dealer replaced it at no charge. I still haven't cleaned up my dusty trunk though.Probably not seated properly from assembly. Their are a few old threads of people complaining about dust in the trunk, they were missing this same cover.