Accidental Deletion of seven bars

Seven bars of music in the middle of a piece have disappeared—for just one Player’s part. (I suspect it was due to over-enthusiasm of vertical engraving adjustments in the part.) The bars are still in the score and in galley view for the part, so I know they exist. How do I coax them to appear again in the part?

Delete that part layout, then recreate it?
(I’m sure that if you post the score, someone will be able to diagnose precisely what happened and how to avoid it happening in future)

Probably quicker to reset staff spacing for that frame (page), by selecting something on that page in Engrave mode and going Engrave > Staff Spacing > Reset…

Yes, but would that explain the complete disappearance of specific bars?

If they’ve somehow ended up off the top or bottom of a page, yes.