I mentioned in another post that I don't think anyone believed Donato was what he was showing (a 30/30 secondary scorer) and his previous track record in the playoffs (19 GP, 0 goals, 2 points) was likely a big reason why he wasn't coveted.
I know people tend to look at Donato on this board like an energy forward with a great motor who started to produce finally but he would often get pissy with refs when he felt he didn't get call, suffered from tunnel vision and his defensive play was inconsistent. If a playoff team wasn't going to use him in their top-6, I think they felt other options were better for depth roles.