disappeared
Banned
Well they do state it's a gambling debt. Gambling could me he took a gamble to change things, who knows.
But Lutece, at the very end, says "Your debt to Mr./Father Comstock is absolved."
Clearly he didn't lose a hand at cards. There's something more to it.
It has to involve Anna/Elizabeth and Columbia. Maybe they/he bet at the fate of Columbia? The fate of his/their daughter?