I have a device that I cannot discover or delete, in observium  Professional

How can I fix this?

mysql> select hostname, device_id FROM devices WHERE hostname LIKE 'ams-sw121';
+-----------+-----------+
| hostname  | device_id |
+-----------+-----------+
| ams-sw121 |       176 |
+-----------+-----------+
1 row in set (0.00 sec)

mysql> exit
Bye
[root@sjc-corp-net01 ~]# /home/observium/discovery.php -h 176
Observium 0.15.5.6406
Discovery

Current Revision : 6406
New Revision   : 7674
WARNING: 0 devices discovered. Did you specify a device that does not exist?
Memory usage: 4.5MB (peak: 4.5MB)
MySQL: Cell[21/0.03s] Row[0/0s] Rows[2/0s] Column[0/0s] Update[0/0s] Insert[0/0s] Delete[0/0s]
[root@sjc-corp-net01 ~]#

[root@sjc-corp-net01 ~]# /home/observium/delete_device.php -h 176
Observium 0.15.5.6406
Remove Device

Device -h doesn't exist!
[root@sjc-corp-net01 ~]#