That's strange, I have found about a dozen of the things. They usually are loot on Lobotomites... :unsure:

I don't throw things so I have not counted these. There is one enemy that drops 8 of them and I have found several other ones. I do find more of the ones that are not thrown. However as usual, I have stopped looting bodies in the DLC so I may not be seeing them all.

Strange, I read that as well. They seem to be every where for me. I think the real delicacies are the Protonic Inversal Throwing Axes instead of the normal Proton Throwing Axes. I have yet to find a PITA, the PTA's are everywhere.

Yes, these are rare, the normal version is scattered everywhere and is easily encountered, but the Protonic Inversal Axe not. I've only found two in the game and at one time a Lobotomite was carrying another one.
The throwing version is also rare, I have no more than 9 of these.

So, I found (3, is it?) 3 PITA's on a Mr.Gutsy in the Meteorological building. I also have one full sized Protonic Inversal Axe that I found in X-13 in the Virtual Reality room. (Which is really cool by the way! xDD)

I like the Protonic Inversal Axe, better than the normal Proton Axe because...well, because it's purple! And it has the world inversal in it, which is cool too. :3

I found about 40 of the regular proton throwing axes and maybe around 15 of the inversal models. I only threw one though just to see how it worked. That one just disappeared after I threw it ... I don't know if it's actually supposed to do that.. seems like they would be easily retrievable.

I think I may have found 60 of the normal ones (though I may be thinking about Tomahawks) but I do think there may be only 15 of the protonic inversal axes.

Proton Throwing Axes of all models explode on impact. That's why they are considered 'rare' as stated by the Wiki.

i havent seen any of the OWB weapons appear on vendors in the mojave either unlike weapons from the other DLCs.