You're not dumb, you just cache in a different way. Most caches I target are not a part of a trail. I wanna know if I have attempted a cache and couldn't find it as opposed to I was never there. It's especially important when you're caching far from hope and don't remember all the caches in the area. Besides, lots of cachers and developers of ALL other caching apps agree that it's important.

But this one is the only app that doesn't have this function. How do others do it? I love DCDroid but I still have to use other apps in addition to it just because it doesn't do this very basic thing.

it's one of the most important features any caching app must have. I'm not sure why it wasn't implemented in the very first version...