Seems media server was not decommissioned properly... Reading your original post - did you perform any other steps besides moving "all the media over into the master server's media pool"?
You will need to have a look at bprd log on the master server to see which media server is selected for the restore.
Based on entries in bprd log we might be able to suggest next step...
For furure reference:
DOCUMENTATION: What is the process for decommissioning a NetBackup 6.0 media server?
http://seer.entsupport.symantec.com/docs/289139.htm
DOCUMENTATION: What is the process for decommissioning a NetBackup 6.5 or 7.0 media server?
http://seer.entsupport.symantec.com/docs/306838.htm