So, the flight exists, but with a different flight number. No problem, right? I gather your concern was over your seat assignments. While seat assignments are not always guaranteed (e.g., for some seats, those with disabilities get priority, even if already assigned to someone else), this sounds like a minor worry overall. I do not understand your concern about your family member's flight. If you're that concerned over the same thing happening to them, just keep monitoring the airline's Web site.