The rev-limiter is a little irrelevant. You posted that the revs never made it above 3500 so why mention it. Despite the rev limiter, they can still suspect that you shifted into 2nd instead of 4th to accelerate, driving the engine way over the rev limiter.
The limiter only limits fuel to the engine, causing it not to drive itself to the destruction, but the tranny is a second device that can drive it to destruction and the only protection against that is careful shifting.
Hope this investigatoin is over and done with soon. I'm sure it's pretty stressful - Good luck!
Cheers,
Harry
