You are sure right about not being able to tell by schematics, whether there are threads or not. I looked at diagrams on a dozen sites, and they all seem to have the same 3x3 inch drawing, with no apparent way to zoom.
If it is threaded, and turned while you were taking it apart (turning slightly so it was out of line with the mortise in the barrel would explain not being able to get the wedge back in), I would expect it would turn easily. Just try sliping a screw driver through the slot for the wedge, and gently try turning it. Easy does it, you don't want to warp the sides on the mortise, just enough pressure it see if it will turn.
Otherwise, you might be better off taking it to a smith. He may have a book of exploded drawings and disasembly instructions, that will include one for your pocket navy.
Or, go back to the Uberti site, and look for a link or phone number that will get you in touch with them, so you can see what they recommend.
By the way, I can see no trace of that "cylinder lock pin" shown in the schematics, on my pocket police ?