Except then your "friend" will say they are traveling and they lost their phone (or it was stolen) and they have borrowed a phone from a friend, so you don't ha

Except then your "friend" will say they are traveling and they lost their phone (or it was stolen) and they have borrowed a phone from a friend, so you don't have a known good number to call them back. In which case still call them back at the number you know is good. If they answer, you know the thing was a scam. If they don't answer, you don't know. Call known numbers of friends and family of the "victim" to find out if they really are traveling. This is not definitive, because the scammers might have called those people too. I think the key to these situations is to ask questions of the "victim" that only the real person would know the answers to. They need to be questions about shared experiences that would not have appeared on social media. If they try to blow you off like "I'm under too much stress to think about such things right now!" hang up. Also, consider asking your friends to let you know before they travel, and arrange with them a pass phrase they can say if they contact you for an emergency. Maybe a duress pass phrase too such that if they say it, you'll know they're in real trouble. Is this a pain? Is it too much to ask of many people? Yes and yes. But this is the world we're in now until we decide to start putting scammers in prison for long sentences.