As your other plays were for NCAA rules, I'm assuming this one is too.
First, golfinref's observation is correct, this sounds like illegal substitution. NCAA rule reference is 3-5-2-d.
Second, there is no rule saying that a ball, not thrown forward, becomes dead when it hits the ground. Sounds like a legal trick play. I seem to remember there was a NCAA game where something like this was run - TXMike can probably provide video
