I'm not sure what context Google provides in those text messages, but if it is just a one-time code; how would I know, you aren't trying to log into one of my accounts?
If not, another one I was thinking was asking them to meet at their local police department and looping in an officer into the story or something. Different things work for different folks so they'd have to get creative to find the right solution.
Oh wait, I believe these are called notary offices in meatspace!
(tangent: at some point I thought that maybe notaries could sign one's PGP key instead of relying on rare/non-existent signing parties)