That's funny ... (realized after you said your screen changed)
Did you look @ the bottom of the screen ... you probably just lost the pinned tiles!
lower right hand corner All apps --> (touch it)
You'll find your Contacts / Photos / Apps, etc
NOW, long press PHOTOS, then select Pin to Start ...
Hopefully, that's the problem ... however CONTACTS are synced w your OUTLOOK account (the account you use to sign in to your phone) & are NOT lost.