Piece of cake - as you know the name start typing it in the small search field and on the third letter (generally) you have a small selection your app included - it took me a while to find and appreciate it - now it's the only thing I use but for special situationsscroll down in the third column to find the application I'm looking for.
Or do you mean that the menu does not change when you put the cursor over the categories in the center column? That's an error, perhaps fixed by right clicking the menu and reloading all plugins.
This could also fix the "not appearing" problem you have (and you should only have to do it once)
hmm I thought at first that you did not find the program at all - if that happens it's probably a flawed installer that does not add itself to the menuMy work around for this has been to remove the mintMenu from the taskbar and then add it again. POOF! the program has finally appeared.
Your error is not unknown and your workaround is correct. It should also appear after rebooting - I'm not suggesting that as a remedy