Answer: Overwatering, or allowing the roots sit in water for extended periods of time, can actually suffocate the roots due to lack of oxygen. You may have fixed the problem in time to save the plant (these are really, really, tough plants - that's why they're sometimes called cast-iron plants). It is possible they re-rooted. In fact, if they still look healthy 6 months after their near drowning, I suspect they have re-rooted. There's not much else you need to do for them. They are slow growing so it may be another few months before you see signs of new shoots from the crown of the plant, or new growth on the leaves. I'd just continue to give them good care and wait to see what happens.
Best wishes with your plants!
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