It is probably what you suspect horn worm, time to go night time hunting. Because of the heat most likely is at night, shine a flashlight and look for glowing and nix em. Slugs do similar but usually not too high up on the plant.

Yah, that plant looks like it might only have one more night's worth of feeding left on it.
Bruce

Did the culprit take all the bottom branches or did you trim those off?
Any hornworms should be easy to spot because there are so few leaves.

horn worms stay on the top of the plant and should be easy to see. looks like grasshoppers. i see tomato plants next to it. you should inspect it for hornworms if there are some lurking. if not then grasshoppers.

use something called BT worm killer, it is a liquid that you put in a spray bottle and spray plants once every 4 or so days or when it rains. it specifically kills caterpillars and hornworms. It is not a pesticide or toxin. It is some sort of anti bacterial that only effects caterpillars. They nibbled on one leaf and die the next morning. I had hundreds of hornworms devastating my tomatoes and tried to hunt them one by one at night as suggested, but could never find them but once, yet I was losing 10 tomatoes a day, full sized tomatoes almost ready to harvest. The one day it stripped my Bhut. I didn't know they like peppers but apparently they attack some peppers. They didn't touch my jalapenos, but tried one of my cayennes and moved on. I guess the heat was too much for them. BT worm killer by green light at most big box stores.

Doubt it's caterpillars. Missing tissue is triangular. Birds? Or something else. Kids?

Did the lower leaves just disappear or did they yellow and fall off? The plant looks a bit yellow. Thought maybe there is (or was) more going on than just a hungry critter.

Steven1032 - no sign of horn worm on the tomato plant.

tsheets - I think the leaves just disappeared. That plant does look a bit yellow, and in fact none of my pepper plants have been terrific producers this year - I got two or three bells from each of my bell peppers, and four or five fruits from each of my habeneros. Really, only my jalapenos are doing well this year.

I'm going to go with small animal that ate all your branches. I also see signs of grass hopper damage on the top leaves. My best guess.