Who was abducted riddle solved (Possible Spoiler)

No one was abducted, the whole story was about an attempt to abduct Nathan by the Serbian so that Nathan's father would be compromised and get him to give the list back to the Serbian, hence "abduction" (the act of abducting), rather than abducted.
Think back. Did they try to kill Nathan in the first half? Not before he got the list himself.
Having said all that it was a rubbish title with no aliens, in a mediocre chase movie in which you feel you've seen it all before.