|You best bet is to contact Seagate and see if they can do anything for you. At least they will know the algorithm that was used to encrypt the data but that is no guarantee that they will be able to decrypt it. It may be that they have a back door password that might work.|
One thing you will have to do is to prove that the data is yours. Seagate are not going to decrypt the drive just because someone with possession of the drive asks them to. Another thing you can be sure of as well is that if Seagate do manage to decrypt the drive they are going to charge you for the service and it wont be cheap.