Phone books don’t show mobile numbers. In Europe at least mobile registries are private and subject to restrictions. Phone numbers are considered personal identification information under privacy laws, because portability regulations have made it possible for people to carry the same number for most of their lives.

Heck, I’m not sure phone books are still a thing over here, but if they still exist they’re not allowed to show numbers for private individuals.

A few years ago there were websites that maintained phone number databases and would let you search who owns a number but GDPR stopped them cold.