You have to delete the inventory references by deleting all the filespaces for the node:
del fi nodename filespacename
where filespace name can simply be an asterisk.
query filespace nodename *
will show you whats there first...
I use TSM 6.3.4 but this should work on any current version. Just be sure that you are ready to remove the client's data from TSM as this is only recoverable by restoring the TSM database.