he may well still have the shits though, just because you saw him out in a car doesnt neccessarily mean he isnt ill,

just make it clear that you saw him if he tries ringing in sick

or do what my boss said to me ( which she wasnt actually allowed to) " if you dont come in disciplinary action will be taken for anyone phoning in sick of xmas period"

as it happened i rang in sick as was in a car accident