Hidden purchases trouble
I can't hide the purchase. I'm use Family Sharing.
On iPhone (iOS 9) purchases don't hidden when click Hide. On OS X Yosemite (iTunes 12.3.0.44) button is not to hide the purchase.
On your computer's iTunes click on the app's top left corner in the Purchased, where the 'x' should be, that should hide the app from the cloud.
Doing it directly on your phone won't work, it will temporarily disappear from Purchased but will re-appear again - that bug was in iOS 8 as well.