How to find Apple Watch IMEI when watch unpaired?

have you read

How to find the serial number or IMEI for your Apple Watch - Apple Support

mind you only cellular devices have IMEI numbers if it's the gps only model it will not have one

I guess he was assuming the article included when the watch was unpaired. You do realize that he, like others here, are volunteers, right? Also, that article also includes a section on finding it from the watch itself, that doesn't require pairing. Or did you not read that part?

Also the serial number will be on the box.

If you ever used your GPS+Cellular watch with a cellular provider you can check with them to get the IMEI.

I

Is/was the watch signed into your iCloud account? Go to https://appleid.apple.com/account/manage/section/devices, click on your Watch, and see if the IMEI is listed there.

He clearly did and answered you. Did you click on the blue link?

And did you look on the back of your watch as the article said?