I am in the beginning stage of a bathroom remodel. I took down the fixture over the vanity and was surprised to find the fixture not mounted to a box. It looks like there may have been a box since there is a round hold in the drywall for the box. Interestingly the same stud cavity is also a cold air return. My cold air returns on the second floor go up into the ceiling and down a center of the house drop to the basement.I am guessing the HVAC guy took out the box so he could close off the stud cavity to use as the cold air return but that does not explain whey the drywall has a hole like a box would have been there.
Is this an acceptable installation according to code??