It might be a bit aggravating to have to do that, but at least you're not locked out of this quest for good. If the Questions and Answers cutscene won’t activate, most players have said reloading a previous save and attempting to do the quest again has helped fix this bug. Radzig has been found in a few other places, such as in Rattay near his room, at the stables at Merhojed, or the horse farm in Neuhof. Players have had problems with Sir Radzig not appearing at the watchtower and not being able to initiate the cutscene at the encampment.
The Questions and Answers quest is known to be particularly buggy. Read this fixes guide to find out how to get around them.