My group owns the parcel at Clear 33, 54, 181. I have a multi-prim house rezzed on the parcel, whose prims I was linking together. After making my last link of a large section of the house, the entire section disappeared. However, it was not deleted or returned to my inventory, and the number of prims in use on the parcel remained unchanged. The house section is invisible, it cannot be selected, and it does not show up with Highlight Transparent. But it is still there, it blocks avatar movement, and you can stand on its upper surface.
If this is a database glitch, please restore the invisible house section, or if that's not possible, delete it to recover the prims it is using.