Venting basement bathroom rough in
With new construction the vent is probably in the wall, you would not be able to see it, it is probably tied into the upstairs vent and may not be a straight shot up, with the home being only 2 years old you should be able to get the blue prints for the plumbing layout and they will show the layout, I would not be concerned because the plumbing would not have been approved prior to the floor being poured without a vent.