Sometimes not saying anything is the right thing to. I usually give them a a howl back, wiat 5 min. Lots of times they show up after just that. Then when i see them i coax them in with something.
If they don't show then i either go to a distress or a ki-yi/coyote distress. The coyote sounds work the best.
Giving him the challage howls is good to, but don't over due it. I like to stick with more younger coyote, in case its not a super dominant male.
DOn't be afraid to give it some time to, howling for me makes me sit longer. I have had them in my lap after my first set of 2-3 howls, other times its been 35-40 min. If i know they are there i give them time, they got all day and i am sure they are not looking for a bullet.
Good luck. Try him tommorow with all the info on here, but they don't always come, and i wouldn't sit in the same spot either. That by itself costed me a bunch one night, there were mad and coming, but i had missed one off that same general side and i think they knew better.