Take page out of trash to reuse
Go into your dashboard > FullSiteMap
You have the option to show system pages, for example the trash.
Click options then check the box next to "Show System Pages"
Locate your page in the trash (It's usually at the very bottom of the SiteMap).
Grab the page icon next to the page, drag it up to Home (Home is at the top of your SiteMap), drop it on top of Home. An overlay similar to the one you see when you are moving/coping a page will offer you the choices to move, alias, or copy the page.
If you want to exclude the page from all navigation:
Once the page is back where you want it. Click on the page name of the page you want excluded from navigation this will open a popover menu.
Select Properties. This will open an overlay with the page properties.
Click into Custom Attributes (the middle tab). Under Selected Attributes you should see a "Exclude from Nav" attribute. Check the box next to it.
If you just want to exclude it from one auto-nav then you might try tinkering with the autonav settings instead.