Can I cap off an air duct in a bathroom?

I purchased a home to flip a few months ago and am having some issues with the remodeling. The home used to have a carport that was remodeled as an addition to the home. One of the rooms is a 3/4 bath directly over the slab. The shower is a door-less walk-out. The problem I am having is there is a vent right where you walk out of the shower. I placed a matt over it to dry out on but when the air is on it moves...lol. I am in the process of gutting this bathroom and the vent is a nuisance. I don't want to put the next owners in the same situation. I was wondering if I could cap it off and tile over it? There is a window in the bathroom as well as an exhaust vent. Note: I would simply move the vent but considering it is in a slab I don't know that I really want the headache and cost. Your input is appreciated.