Just to follow up my own question. You can re-assign a storage location or delete a user when the original storage location is no longer available using the
DLOCommandu.exe command line tool, located in the BackupExec install folder. The DLO help file outlines each command line switch. I was able to use this tool to move users to a new storage location after the old location was not able to be brought back online. I was also able to delete some old users as well, which the GUI admin tool does not let you do if the location is unavailable.