I'm afraid you'll need to escalate this to your SEE Admins for file recovery, and hope that they had a Master Recovery Certificate setup and applied. There is no other way of recovering the files other than that, or remembering the password (though finding the original always helps).
If you're not after file recovery (i.e. you don't want the files back, you just want to free up the space), then you can just delete the encrypted files.