You're touching on a very problematic thing here, the warranty does NOT cover physical damage to the product, this goes for ALL smartphones not only Asus. You don't have to drop the phone to crack the screen, it's also enough to have tight jeans and apply a lot of pressure on the phone itself. It does sound like a physical damage thing, however it could be manufacturing error, as seen with the S20 ultra glas on their cameras, that being said u'd have to make a case for why it could possibly be an issue caused by a manufacturers defect, it doesn't need to be proof, it just needs to be an explanation as to how it could happen without external force, then the burden of proof would lie on the service center.