sorry about the photo. This one should work:
https://www.extension.umn.edu/garden/ins ... 4-1-lg.jpg
parasitized hornworm with braconid wasp cocoons.
And no, you would have to be watching very closely to ever see the braconid wasps . Braconid is a family name and there are a number of different ones (which also attack things like cabbage worms, etc). The specific braconid that parasitizes the hornworms is about 1/8 of an inch long.
You can order them commercially, but if you have the right flowers for them, you shouldn't have to. If you don't have the right flowers for the adults, once they emerge from cocoon, they won't stay in your yard anyway.