Lost my badass rank and all my gold keys too

Is there anyway to fix this?

For your keys and customizations (shift redeemed customizations), send in a support ticket with Gearbox here
https://gearboxsoftware.zendesk.com/hc/en-us/requests/new

As for your badass rank, make sure you are connected to the internet. Then load up each one of your characters one after the other.
That should restore most of your lost rank.