Have you tried hitting Alt (or X in Linux)?
If you are playing on PC, do you have a controller you can try, to see if the area search function (holding the A button) will include the head in the results? It doesn't for normal NPCs/animals, but is worth a shot. Facing the head may work to select it, as well, even if he can not be selected in the keyboard/mouse UI.
If that doesn't help and you are playing on PC, please reply with your save (or a Dropbox or Google drive link, etc). If you are using any mods, also include a list of those enabled and/or the modsettings.lsx from your profile folder.
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin Enhanced Edition\PlayerProfiles\<ProfileName>\Savegames_patch' folder.
In Windows Explorer you can zip a file or folder by right clicking on it/them and selecting 'Send To | Compressed (zipped) Folder' (and similarly in OSX/Finder).