I just read somewhere on a website that a school received a secondary violation because a recruit made an unannounced visit during a dead period. An assistant volunteer coach was in attendence and obviously not aware that this was in violation, and more than just a hello took place. He received a warning, while the recruit was declared ineligible. They did not say in which sport this occured.
I doubt very much this was baseball, but regardless, always a good idea to call in advance to let someone know you are coming if you are not familiar with recruiting procedures.
Original Post