We entered Cracked Tusk Keep and killed Ghunzul before we got Silus' quest for the pieces of the Razor. The UESP says that the quest will therefore be impossible to complete. The quest arrow points to Ghunzul's dead body, but he does not carry the piece he's supposed to.

This feels like a pretty serious glitch. Has it been addressed, and if not, does anyone know of a workaround? Thanks!

If this still occurs with the latest patch (1.9), then was most likely something that Bethesda never addressed. Unfortunately, since Bethesda isn't going to be doing any more patches at this point, your only option is probably going to be to load a save prior to killing Ghunzul.