It seems far fetched to think that the UAE would take a sudden interest in the security of Portland, Oregon but perhaps that's possible. What IS impossible is that a country that's a client of the US would dare to hold, let alone torture a US citizen for a 106 days without the explicit approval of the US.
You think the guy's story is far fetched because he just happened to be in the UAE. Not so much, really. They keep track of the movements of many people (1.5m according to Citizenfour) so they would have known that he was in the UAE. At that point it would only have required one bright bulb at the FBI to come with the idea "hey, why not we get our buddies in the UAE to have a chat with him?"