They didn't get anything reversed with TO - they filed a grievance, but SF rescinded their trade and sent him to the Eagles where he wanted to go, but he should have been a free agent and never was. That was actually part of his eventually blow up in Philly, because since he wasn't actually a free agent and had no leverage based on how it played out the Eagles signed him to a contract extension that was very, very team friendly. And in TO's case, there was actually a legitimate dispute about the deadline. This was just a pure eff up.
And I'm sorry, but while the agent may have made the ultimate error, if Dumervil was really the "ultimate team player" he could have agreed to a deal sometime before the last day. Agents still work for players, not the other way around.