Their stories are not only incredible, they can offer no details to back them up. When pressed for more information they will change the subject or seeing that they are cornered, they will leave. They may change their handle and come back - or they may move on. Inability to provide information. However, after a period of time in speaking with someone, you do want to progress to a point where you can get to know them better.
Minors often have their own telephone numbers.
They will give out that number pretty fast. These are questions that will invariably stump a teen. Asking for one's political affiliation is a clincher I've recommended many times. Declining to state political party is one thing - not knowing what a political party is is quite another. Try to elicit adult answers to adult questions and failing that - walk away.