Could the owner-registrar of the domain lose ownership of same?

Yes, in any of the following circumstances:

1- When you lose a dispute about the domain in a case handled by the ICANN (the body in charge of overseeing the global domain registration system). In that case the new owner will be the winner of the dispute.

2- When the payment is not valid, is returned or is fraudulent. In this case, the domain will become property of MrDomain.

3- When the domain expires due to non-payment of the amount for renewal. In this case the domain will remain available.