The volume was not deleted because an image mode copy might contain inconsistent data.
Make sure that you specified the correct volume. If so, wait for the restore operation to complete, or cancel the restore. Use the management GUI or the lsvolumerestoreprogress command to monitor the progress of the restore, or the restorevolume command to cancel the restore. Alternatively, specify the -discardimage parameter to force-delete the volume, canceling any active restore operation.