It might be too late, but there also might be programs that have lost pitchers due to the draft, injury or transfer. If you son has already enrolled at a school, perhaps your coach (or travel coach) could call and see if your son could get a try out. Contact coaches he has worked with pitching wise, baseball is a small community. Our son decided to go JUCO, but just yesterday signed his NLI to play at a DI. (It's not a top 40 razzle dazzle school, but we think it is a good fit) He graduated in June, and really exploded late in the season and over the first part of summer. So it can happen.
Prepster's situation is not unusual. Our hs coach promised a player who wanted to walk on at his college that the college coach had been contacted. After the tryout, the college coach said to the player, "If I'd known you were trying out, I would have saved you a space." We team parent heard the story but didn't really believe it. Until it happened to others. The hs coach has lost so much credibility that he could have Derek Jeter to shop around and no one would believe him!