OK, my first question when asked for details is this. Do you have a DBA where you are at? When the Oracle database was set up was archive logging turned on?
Basically there are two ways to restore, the first is from backup, which obviously you do not have, another is by rolling back using the Archive Log. I know this based on the first Administration class on the DBA track, but I never got further than that class, so the exact tool and steps to recover, I do not know, a good DBA would know this?