[wadew2lt]

I know this piece. I had the plastic wheel well off early after I purchased my car. That, my friend is a spacer/insulator that fits between the fender and the bracing behind it to give a small amount of support behind the fender to prevent what some body men call "tin canning." The bend closest to your little finger on the second pic, goes up against the sharpest bend of the fender where it goes from horizontal to vertical. If you found it near the bottom of the fender, it would be because it fell from its upper position. If you remove enough of the fasteners in the wheel well, you'll be able to see where it fits vertically. (long edge against the inside of the fender.)
Hope that helps.