I have an app open and running but not visible on screen

[iMore Question]

I have been using an advent calendar app until 2 days ago when, after restarting my macbook pro it disappeared! It is still running but I can't make it visible- no zoom option and resizing the screen has had no effect. Using OS X Yosemite

 

[Just_Me_D]

Can you not reinstall the app to see if that'll help?

 

[Ledsteplin]

Check all your folders.