There isn't much proof an SS will do of you being in CoF. Anyone can enter CoF and SS and then say the same. The only proof that could be provided would be a video, which obviously isn't happening. I have never had that happen to me on any map and I can safely say I have been to every single map available in Nation Wars. Im not saying I dont believe you though, stranger things have happened in PW. Hopefully this could be looked into and is a one time thing.
Its a known game bug ......It happened in official PWI too. If you have done the cube prior to NW and still had a quest running in your quest log (i.e.defuse the bomb), and you get killed in NW, it will teleport you back to the Cube of fate.I am not aware whether it has been fixed in official PWI.