You can do a master reset to restore the menu missing items. However, it will erase ALL data and restore it to like-new condition. Anything saved will be wiped out and you’ll be starting over.

Here’s the instructions how to do that; it takes only a minute:
http://support.garmin.com/support/searchSupport/case.faces?caseId=%7B94841fa0-ca0c-11e0-cf56-000000000000%7D

Here’s a video on how to do it:
http://www.youtube.com/watch?v=r7e_9cDQH_M

As for the other issue, you won’t need to unmark anything if you do a master reset; it will all be erased.

However, if you choose to not do a master reset but want to find a cache that was inadvertently marked as found, there is buried in the menus “show found caches.” You could then see it and navigate to it. Can’t recall exactly where the “show found caches” option is; I’d have to play around with one to find it. I currently use an Oregon but used to use a GPSMAP62s.