virtualbox - I couldn't find some softwares after installation on unity search

I installed VirtualBox via Ubuntu software center on Ubuntu 16.04 but I couldn't find it in search. So I search it through disk and I find it. My question is why this happened and how to fix it. I installed some softwares and some of them will appear on search and some not. I am using Ubuntu software center instead of Ubuntu software ( because it couldn't launch).