Until 1970 the Man Booker Prize had been awarded to a book published in the previous year, while from 1971 it was awarded to a book published in the current year. Therefore no prize had been awarded to a book published in 1970. The Lost Man Booker Prize was thus a special edition of the prize awarded by a public vote in 2010 to a novel from 1970.
A longlist of twenty two titles was drawn up by organisers. A shortlist of six was selected by journalist and critic Rachel Cooke, television and radio presenter Katie Derham, and novelist and poet Tobias Hill. All three panellists were born in (or around?) 1970. There was a public vote on the Man Booker Prize website, March-April 2010, and the winner was announced in May 2010.
See also Wikipedia
Article and longlist in the Guardian