Short answer Replace the plug!
Without the ground plug you are breaking the connection between your coach and the campground pedestal plug which is eventually wired to a ground rod buried on site somewhere. Without that connection if a 3 pronged device shorts internally in your coach and someone touches it... Electricution can happen.
That ground plug was added in the early days of electricity to prevent electricutions.
If it was me I would replace the plug no hesitation!
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