In their defense, even if he did try to get custody it would be next to impossible in most states.
I know here in Georgia, you have to practically drag the judge to down to witness for himself the mother smoking crack while having an orgy and physically beating the s**t out of her kids in order for the father to get custody. Sad, but unfortunately true.
ETA: even if he is fighting for custody, it can take YEARS. Family court moves very slowly.