Open Potlatch (the [Potlatch 1](//wiki.openstreetmap.org/wiki/Potlatch_1) (via the Edit tab) tab and manual URL editing) for a particular area, and press U (for "undelete"). This will show you any ways that existed but have since been deleted. You can click any of them and 'unlock' them, then save, should you want to restore the ways.

Open Potlatch (the Edit tab) for a particular area, and press U (for "undelete"). This will show you any ways that existed but have since been deleted. You can click any of them and 'unlock' them, then save, should you want to restore the ways.