Excellent hike, an absolutely incredible canyon.
However, the map you are showing on the hike description did not match up with my experience. I thought I had missed Peter's caves somehow so I decided I'd just continue as far as I could get today down the canyon and try to find it on the way back. I ended up doing a substantially dangerous climb to some cool looking caves, which it turns out didn't match up with the pictures of Peter's Caves.
However I was surprised later to find Peter's cave, the unnamed cave with a wall and the secret tunnel entrance (ruin?), several other caves not mentioned, and the waterfall.
Peter's Cave (the larger of the two) seemed eerily similar to Herman's Cave, I can see why they named them after members of the same family.
I also found: trash, a Coleman cooler, a shirt, a grill, the remains of a pair of jeans, and some shoes which could have been Petrarchs originals since they must date back at least 70+ years. I suppose if I had started the hike naked I would have been well-equipped by the time I finished
I got to the waterfall but turned around there due to time, I'll have to return from the opposite direction to finish the loop. I have no GPS but I estimate I got about to the point Peter's Canyon Trail forks south and east (both named the same trail?).
Also, the shortcut over to Tortilla creek you indicate is indeed a viable route, it's just nowhere near the waterfall (unless there was a different waterfall I didn't see.) A slightly easier route is to go northly (northernly?) from an eighth of a mile west of where you indicate to leave Peter's Canyon.