2 respuestas
If they were working in a Sandbox, you can access that from Setup > Data Management > Sandbox. If you're an admin you should be able to log in there. Depending on when the sandbox was last refreshed, you might have to use an old password, but it should work.
if they were working in a Developer Account, without knowing their login information, you really can't get in there.
Can you go to Setup > Deploy > Deployment Connections. There's a chance that will show you any external orgs (i.e. Sandbox or Dev Org) connected to your production org.
