What about an aerodynamic modell in your Sim with total loss of flight controls ?
That is in theory the easy bit. If the sim has been qualified to the relevant standards then the flight model accuracy will have been checked, and whether the controls are moving or not shouldn't be an issue. I might have some doubts about very long period motion, since most sim checks are on a 30second scale or so, but frankly that applies to the normal configuration too.
I'd be much more wary of the system simulation, personally. It's much harder to get that right for the sim builder, because they are usually working with just technical descriptions for any simulated kit, and dependent on ICDs for any stimulated stuff. Are you sure there wasn't some part of the system working that shouldn't have been. Do the unpowered controls lock or float? Which did they do in the sim? And so on.