Signed up via Facebook
When you signed up using Facebook you should be able to see your friends that use Hold automatically in the highscore.
Signed up via Google
When you singed up using Google you will be able to connect with Facebook directly in the highscore to see your friends.
Unfortunately, we don't always get a good response from Facebook's API when asking for a friend list, so it can happen that you don't see your friends.
If you try to refresh the highscore, or try to switch the time filter (Day, Week) you will hopefully get to see them again.
If you still have a problem, just drop us a line and we'll do our magic.