doctor who - How does the shop owner in "The Bells of St. John" have the number for the TARDIS?

Or perhaps it was Ace?

For those that might not know, Ace was the last companion to be on the classic show, not including comics or the TV movie, she ran with the Seventh Doctor, and in the comics, it was said that:

^{[SPOILER ALERT IF YOU WANT TO READ THE DOCTOR WHO COMICS]}

That she went to the Academy on Gallifrey to train to be a Timelord, which if you're on Gallifrey, it should be easy to track down a Tardis, especially if this Tardis was in a Museum, stolen, and is being used by possibly one of the most famous Timelords, it should be rather easy to find the number. Also, she was, to my knowledge, evacuated and brought back to Earth, before the Time War ended, she was hinted at being alive in a Sarah Jane Adventures episode, so maybe it's Ace!