> could have involved the use of your phone number to send and receive phone calls

Surely from their logs they know if these calls/texts happened?

If, during that period no calls/sms's occurred, then there has been no breach - the attacker was close to their target, but walked away with nothing.

If messages/calls were made, the user really needs to know who they were to/from to make any informed decisions. And Google has those logs.