What do you mean? Missing is handled within nzb360, just in a slightly different way. Any movie showing in the Wanted tab is missing and either soon to be available or already available.

I did it this way to help manage a ton of movies on mobile. Instead of seeing ALL missing on the Wanted tab, you only see movies that are releasing soon (or have already released), to cut down on clutter. All of the missing movies are available in the ALL tab though.
Like on sonarr there is the missing tab, I like to not monitore movies and just download it, so having a missing tab would be much more easy to find the movies I have missing instead of going to all tab or going to webui to the missing tab.
The Wanted tab is essentially a missing tab, except it doesn't show movies that aren't physically available any time soon (which means there won't be releases).