Lost all my contacts rather suddenly. Currently backing up but will it work?

Hi everyone,

A few weeks back my iPhone 4 got stolen (and is now in a Lost Mode wherever it is) so I bought a new iPad mini. I set it up with an old iCloud backup and thus it had all my contacts, notes, reminders etc. Yesterday all my contacts suddenly disappeared from my iPad and an old iPod which had the same contacts list on it. I tried backing up the iPad again to the iCloud back up and it is currently restoring. What I want to know is will my contacts come back? And is it possible for someone to have erased my iPhone while it was in lost mode resulting in my loss of contacts?

I'd really appreciate the help.

Thanks in advance!!