[forgotmypw17]

I promise you, this exact thing happened to me.

I had never used my number with an Apple device, I only registered my email and FaceTimed someone.

Maybe I gave Apple my phone number at some point.

One day, I looked at my Apple device after not using it for a while, and discovered a handful of text messages which had been forwarded there -- you're right, to iMessage, not FaceTime -- on the Apple device.

I never received them on my actual number.

[ThePowerOfFuet]

Everything I know (and my expertise on this topic is pretty good) indicates that a phone number cannot be registered for iMessage without a SIM carrying that number being inserted into an iPhone or iPad.

Other devices signed into the same iCloud account can then use that number as well.