First of all, definitely put in a letter of complaint to the director. IMO, leaving a child sit in his own vomit is not acceptable. Neither is the excuse that they were too busy at that time of day to see to him. I have my DD in daycare part time, so I know that at that time of day, it is really busy, but that does not mean that they can not attend to him when he vomits, or at least check that he is ok.