Well the report sure does only tell me she had a lot of undigested bulked up roughage in her system. I haven’t heard of roughage killing a bird, although I’ve heard of intestinal blockage.
It did say there was grit present.
A lot of birds don’t eat long grass, but some do. Looks like maybe this bird liked to eat long grass or something very fibrous.
You may want to try to figure out in your yard or pen what that material is and mow it down or remove it.
Sometimes no amount of grit can handle that.
For your grit you should be using something like this if you aren’t already. It’s like small pieces of granite stones like the size of half of a pea.
https://www.mannapro.com/products/poultry/adult-poultry-care/poultry-chicken-grit-probiotics
ETA: Gosh I’m not sure about the miners lettuce..everyone in ncal has that stuff around...unless it was a very big mature weed and she ate the whole stalk.
Don’t be surprised if Davis cant tell you what material it was, that may have been long disposed of, but they could possibly have made a note.