That's a really interesting story!
I've noticed similar strange numbers appearing from those who call from a VoIP service like Skype.
One heuristic I use when I see a call from an unrecognizable number is to drop the first call and take the next one (if it comes). Well meaning folks, usually will retry in a short while, while scammers will usually move onto the next target.
I take the "if it were important enough, they'd have left a voice mail" approach to phone screening. I won't answer any number I don't recognize, but will immediately call back after hearing the voice mail.
Maybe it is my provider, but I hate voice mails because the I have to navigate using button presses and constantly wait until it is done reading things back to me.
I take the "don't check voice mail ever, and disable it if possible" [1] approach to phone ownership. These are broadly incompatible in the same society.
[1] Oddly, on my last phone, with T-mobile, disabling voice mail wasn't possible through their internet account management. I did manage to get my voice mail disabled, but I had to call them and complain until they agreed to disable it.
