Why was Carlisle not mentioned in The Doomsday Book?

because at the time it was in Scotland

https://en.wikipedia.org/wiki/Carlisle,_Cumbria

The original manuscript of Domesday Book consists of two volumes, of which the second is devoted to the three eastern counties, while the first, which is of much larger size, comprises the rest of England except the most northerly counties. Of these the northwesterly portion, which had Carlisle for its head, was not conquered till some years after the survey was made; but the omission of Northumberland and Durham has not been satisfactorily explained. There are also no surveys of London, Winchester and some other towns.