I think that SM were not as developped as they are nowadays.This point (re: they know his phone number) is sheer brilliance in its simplicity.
What else relating to phones, digital media, text messages etc do they have?
I also think that it was a burner phone, never reassigned and I speculate that Portughese carriers have destroyed the records of 2007 because of privacy laws.
AFAIK, in France, carriers can conserve your personal data (messages, phone logs...) for a year only. I don't know about Portughese laws in such matter, but their privacy laws are much stricter than the US laws.