That looks like mine that I found under my seat. Although mine is in a little rougher shape. At some point a mouse took residency up in the rear seat and was starting to chew the build sheet up for padding. I noticed bits of it after a long winter and investigated. I now have the majority of the build sheet and no more mice. I put the sheet on some double-sided tape to hold the pieces together. Parts of it look like a puzzle. But what the hell, it's there.
