Sorry to hear that man. I've got two pugs myself and they are my kids. Been with me through all the good times and the bad. I hope the ex is at least treating the dog well and at very least has a happy life.
That's all I've ever wanted for my dogs, is to make sure they're taken care of before me. Had a scare once where one of them went missing for about 6 hours. Worst day of my life.