You probably have auto-registration enabled; it will have re-added itself to CUCM when it attempts to register in between you deleting the phone, and re-adding it.
I would either:
- Disable auto-reg (on your System/Cisco Unified CM) page
- Find and edit the auto-registered device rather that adding a new one
The issue that I can't find the device itself in the CUCM.
By the way my device is a third party so when I'm trying to add it I got the mentioned message.
Can u go through this DOC and run SQL query if it helps for 3rd party phones.