DOES ANYONE KNOW HOW TO TRACE THE ORIGIN OF A FAX (FAX #)?

I have fax running on my xp home system. I am getting fax
receiving falure messages all the time. I checked the
phone line, modem and even had the local
telecommunications company check the condition of the
line. Everything is fine.
I receive most of my faxes, but I am confused as to why I
don't receive them some times.
DOES ANYONE KNOW OF A WAY TO TRACE THE ORIGIN (FAX #)
OF A SENT FAX.