Can you check Auto Saves and find the most recent one where you could freely move between Wyrm's Crossing and the Lower City? If you can identify this save, it might be faster (in your case particularly) to start there as you are correct you're looking for a needle in a stack of needles. And you'll lose some playtime but it may be less than going house to house looking for a corpse, especially if some of the corpses disappeared by now and just left pouches behind.
