I get this problem as well.
I think most of the time I just use the create colony button so that it shows up on the Economics window and interact with it that way.
There are some alternatives: You can use the checkbox 'Centre on Selected Body' to find it.
You can look for it in the Minerals tab in the main window, as long as you are in that system.
You can look for it in the System View window, which is easier if you use the settings to only show moons with minerals.