This sure does look like a sliding door lock. And the interior knob doesn't line up with the exterior key hole which seems to be much higher.

Is there a manufacturer or part number on the lock anywhere? If so, try and look it up online to see if it's even made for this use. Normally a hinged door has a latch and strike plate separate from a deadbolt. It's hard to tell from your pictures if this is even a standard mortise lock opening. If it is you could replace it with a proper lock.

It's almost as if they took half of a sliding door and mounted it on a pivot hinge.