OS,
Many college players at some schools going into their third year don't even get summer assignments. Mine got two summer assignments, his first, he didn't go, second year he went and third he wasn't placed or offered. Wonder why, because they didn't expect him or the others that were drafted to be available in the summer. If you were drafted and not sure as to what to do, they will place you in a summer league for you to show your stuff a bit longer until you decide what you want to do.
I don't think this is unusual.