IMEI number

Are you sure it’s a cellular model?

Does the crown have a red ring on it? If not, it’s not a cellular capable watch.

From your watch, go into Settings, > General, > About and then scroll down quite a ways, it's there.

From your phone, go into the Watch app.

Click on "All Watches" in the upper left corner.

On the next screen, click on the letter 'i', it's there

Doh! This might explain why it can't be found! My bad! Thank you for chiming in! ;-)