Actually the anchor bar is still there, you can see it in the photo. The "plastic" casing fell out, it's a cheap and easy fix.That's more than a cheap plastic piece. It's the anchor for a child seat, and is a little more than a pop-in, falls-out part.
That whole rear panel on the seat is a snap-off part, with clips on the bottom and a retaining lip on top. A local boneyard/parts recycler may be a good source of that whole panel, with carpet and both of the anchors still in place. The whole thing shows for $168 new in the linked parts page, giving you new everything. Get the clips/retainers for the panel at the same time in case they are damaged on removal.
Insane how a piece of plastic costs over $100 new, right? It's a plastic garnish.Can you give me an idea on part # and cost? Where I might get that?