Offer a reward....A loose guinea is hard to catch...My hubby is super fast but the loose ones out ran him.... He even offered folks$5 a guinea to round up some of our loose ones and put them in a mating cage....he never paid up. Finally the loose ones flew in the cage because they heard the girls calling them.
First put the dog in a house or something because right now that guinea doesn't want to come home...He's probably shook up.
Then an ole timer told me to catch any bird, you get like a cage with no bottom in it....put a lot of feed in it, did a small tunnel hole on it and the fowl will go in but not out. Probably tru with a guinea, I've seen my guineas fling themselves against fences when they could have just flown over.
Good luck.... If you were closer, and you might be ...are you in GA, I have some keets that are male.....