Interesting story and I admire your honesty, as I’m sure that most people (not me of course 🤔😂) would have just returned the car with the two keys, in the knowledge that nobody would be any the wiser as the cars are generally binned off at auction, sold as seen.
As long as you intend sticking with Motability then all should be well, but if you ever intended leaving then it’s a shame that this will cost you your no claims history, which would have transferred with you to a private car. Unlike private insurance policies, with Motability we don’t get protected no claims discount.