He might have touched the door or a door knob or a railing or a wall or somewhere that vomit had been splashed
he might have walked through that nasty pavement outside where some idiot hosed down a puddle of fomite breeding vomit- and then gone home and taken off his shoes
This is not cholera (bacteria) or anthrax (spore and bacteria). It doesn't breed anywhere except in certain mammal cells although it breeds well in those cases. Elsewhere (e.g. puddles of vomit), it waits around to die. That might takes hours or days but it will surely die.