So, in a way, all the currently living Doctors (except Christopher Eccleston) found a way to be involved with the 50th anniversary! I think that's great! Especially since Sylvester McCoy was working on the Hobbit at the time as well.
That would actually be really cool if they were in the special, but I think they were, they were under the white tarps were the statues were in the art gallery. You can tell because of Sylvester Mc coy height clearly stands out than the others.