Yes, lion9car is correct. First, I’d have all 4 inflated then watch them closely. (I once had a oil change place drop my tires from 35 recommended to 25, and another time a neighbor kid thought it’d be funny to deflate a tire.)
Does your dash show tire pressure on the fly? (I ask b/c I was surprised mine shows TP, updated every minute.)
It’s possible the tire was deflated when you picked it up. If not, this is something the dealer should repair, if they can’t find a puncture. Modern tire/wheels should lose pressure only with temperature changes.