I've read about this scam and it seems interesting to me - is that a realistic thing that might happen if your relative lost a phone? Perhaps it's a market-specific issue, but I have had multiple phones lost/stolen/broken in my life, but I still have the same number I had since my first phone back in the previous millenium, and I somewhat expect that some kid's phone number will stay the same until they die unless they move overseas and get another phone number there (and probably still keep the old one as well). Don't you have number portability across phones and carriers?
We've had total number portability here for a few decades, but I do know a few people who have changed numbers due to lost/replaced phones also. I'm not sure if the reason for this is due to unawareness of the process, difficulties proving ownership of the previous number, impatience (new accounts are activated same day, number porting takes 2-3 days), or some other factor, but even when the option is there it seems not everyone avails of it.
Yes portability etc is a thing but this is targeting trusted relationships and non tech-savvy folks. It’s also really easy to do and doesn’t need many to so a different phone number can be explained well enough as ‘a friend’s phone’ or even just ‘my old phone broke’