If I perceive an imminent likelihood of an attempt, I'll generally start trying to get a location from them - it's not subtle, they'll know. Sometimes people will give it, other times they resist for whatever reason. For those that resist I will process that feeling that they have and then try again. They may even ask if I'll contact police, in which case I can't lie to them. Ultimately I may _never_ get a location, or I'll have an extremely ill-defined location - it's always up to the caller if that is information they want to give.