Finally after several years of waiting, I finally achieved success; counted as many as 18 caterpillars on my common milkweed.
May be a common observation, but I noticed they move around a lot, and many disappeared for most of the day, no where to be found on the milkweed, only to reappear in the later afternoon. I found one on an adjacent purple milkweed one day.
Unfortunately, I do not think any survived. A large flock of grackles/starlings descended, and when I looked later, not a cat to be found.
In past years, I could sometimes find large aggregations of Monarchs the last week of August at a remnant prairie site. No luck this year, will try again tomorrow.