Sorry but very niave to think you'd get him back after this length of time... asking a comparative stranger to 'board' your dog until you want it back is asking a hell of a lot...
your ex is obviously a total liar, oh well, learn from that one...
the guy who has him now has every right to keep him (possession is 9 tenths of the law etc etc) dogs are treated much like anything tv's, washing machines, stereos blah blah blah unless he stole him and you can prove it? but you'll have a right nightmare trying to get him back and the the dog may be perfectly happy where he is even if you're