I agree, there is probably a Factory Image in that partition which might have been used to reset your system back to factory specifications.
There are normally two ways to use the image. The first is a OEM process that usually includes holding some key while turning on the power. Have you tried that? In some cases, the 8.1 update process broke that, but it may still work.
The other way is to use the Windows 8 Reset, which I think you said you tried. Depending on when you did the update, that may or may not work.
If neither of those work, then we are back to needing Recovery Media. You do not know anyone that has a functioning Windows 8 system? I suppose a Recovery Drive made on another system will not allow you to sign in on a different system, so that may not work. But install media will, Windows 8 or 8.1 hopefully