That sort of thing is fairly rare ... especially with guys who actually turn into decent prospects/players. Usually, if there is any fear that a kid won't sign, the team will deal his rights (see Tim Erixon) rather than lose him for nothing.
For me, the important thing here is that, we are starting to see more of our draft picks getting signed. Which means that, in some realm of possibility, there's a chance that they will not only play pro hockey, but will play in the NHL. That's a sign of improved scouting and development.
Exciting stuff ... congrats to Kerby Rychel!