Well, Susan got dragged off round the universe by her grandfather when he left, and was eventually ditched on 21st century Earth after a Dalek invasion because the Doctor reckoned her current boyfriend was probably better for her. This means that Susan probably spent a good while stranded on Earth trying to pretend to be a perfectly normal human before getting back to Gallifrey, however that happened.

As regards the Rani, the "being lost" line might refer to her exile from Gallifrey, presumably before being called home for the Time War.

I am half tempted to write three different Woman-in-White point of view fics, one for each possibility.