Unlike GD where you need some type of face-to-face (scouting trip, HV, or CV), HD only requires that you have a scholarship offer and some minimal effort level (a promised start or some level of minutes can work in some cases). If the recruit is considering just you when signings start, he'll sign with you as long as its legal and the AD lets you (i.e. he's a similar type recruit to the rest of your team and you aren't exceeding the max of 6 recruits in any one class).