Do you still have the old database? You should be able to move your instance around as long as you have a dump of your DB, that's where all the keys of each community and user in your instance are. Those are the ones telling other instances you're actually you, if you loose those I don't know what can be done so other instances flush your old content and treat you as a new account. But I would count on thi s being a feature since it could lead to people impersonating someone else if they get a hold of the domain without the DB.
EDIT: amm, maybe I didn't understand correctly, are you trying to move to a new domain? Or to a new server with the same domain?
What's re-home?