Surely 200 years of weather and tourism would uncover some??
In: Other
Here’s a [article](http://science.unctv.org/content/so-what-happened-confederate-dead) that will answer your questions regarding Gettysburg.
Skeletons decompose just like the rest of the human body. If any soldier were left on the battlefield or buried in shallow graves, their bones have long since disappeared. It takes bones about [10 years](https://www.scienceabc.com/humans/skeleton-mystery-dont-bones-decay-decompose.html) to decompose.
They were _buried_ in actual graves. Not right away, but eventually.
Were you thinking the bodies of the dead were just left outside?