What happens to Benjamin when he tries to escape from slavery in the book, Incidents in the Life of a Slave Girl?

Benjamin made it to the North on his first attempt, but was captured and returned to the Flints. He was then put in jail and suffered from the horrific conditions. After that, he was sold to a slave trader who promised not to resell him until he reached New Orleans. Benjamin escaped again and fled North. Philip runs into Benjamin in New York and that is the last time he is heard from.