While applying dynamics, my staves clashed. I went into engrave to move the staves and one staff disappeared off the page. It still plays, and is in Gallery view, but I cannot see it in page view. I deleted all dynamics, but it did not move back.
Welcome to the forum. Really, we need to see the document to see what has happened.
Obviously, you’ve made some manual adjustment to the page layout that is not what you intended.
It is possible to Reset the Staff Spacing, in Engrave menu > Staff Spacing > Reset Selected Systems.
That worked, thanks so much!