While DCS Mark Twigg was hopping mad, Rufus was hopping on the Metropolitan line heading for Finchley Road. He was on a kind of pilgrimage to the scene of a crime or two, Marcus's house.
He was aware that the house had passed on to a relative, but he wasn't sure if that relative still lived there or had sold it on. Either way, he wanted to go back to where he was reborn. Mac2 had been instrumental in persuading Rufus it would be good to go back and 'find himself'.
Mac2's self-preservation circuitry had a homing instinct too.