Too tired to post yesterday, but nothing new to report anyhow.
Today, I was going to get on my hands and knees again, but I found the chain as soon as I walked up to the bushes. Right on the ground in a little pile, two feet behind where I had been holding the saw. It was on the grass surrounded on 3 sides by the bush bed, and obscured by a bush when standing right above it, but not from the side where I had also stood to look before.
This time maybe the sun was in the right place, because the rivets were very apparent.
Not broken, not rusty at all after three nights.
When I got the saw second hand, it wouldn't cut, and when I went to sharpen it, I realized it was on backwards. I hope I get it right this time.