Use whatever it's there.

Existing got wet and I had to throw away. It was Kraft

Buy the same one same R-Value most likely it's R-30 and put it in where it's missing.

This is in the ceiling of the garage, directly underneath a bathroom

Is there a room above the garage? If that is the case, I have always seen the kraft facing down. In Any case, put it up the way it always was, so it matches what is in the rest of the ceiling.

Kraft paper should be on the conditioned side, as it's a vapor barrier. Unless your garage is heated, that would be up.

It doesn't really work to put it in from below, because you should staple the kraft paper on the joists under the floor. Since you can't do that, I'd use unfaced.

Why make this complicated... If there was a leak only a small portion of the ceiling is open, so the only insulation that needs to be replaced is probably 1-2 bays a few feet of it. Just put the same insulation you had there before the way it was and patch the ceiling. :-)

Yep, whether it was right or wrong. Its only a small area, and the way it is, worked before, so no reason to change one small area.

@Stax Who said anything about original insulation was installed the wrong way?

Unheated garage, house is directly above it. Took down drywall that was on the “ceiling” to find wet insulation because it was directly under the toilet.

Also I’m considering putting styrofoam board up instead of drywall. Would that be ok? I’m not at all concerned with the aesthetics of it all.