DBs Connected Accidentally

Alright, so here's the deal, I have a site which uses PhpFusion. Although, before when we want to add something, we usually do it on the test site, which has a completely different database than the actual site. Today, an admin accidentally copied every folder from the actual site, to the test site, and the result was, that both sites connected databases.

When he went on the test site, he noticed that all of the members were automatically joined into the test site, and he deleted them all. Deleting the members from the actual site as well. Everything that is done in the test site (Posting news, forums, deleting members) is mirrored in the actual site now.

I know I have lost the members he deleted, and it can only be fixed by using a backup. But how can I change the test site, back to it's actual database?