There is, of course, a possibility of that kind of damage occurring without anything like a drop or impact. But it is highly unlikely given the nature of the damage and its location. Your problem is that you are going to be working against a corporation that really has no reason to believe you, not even in the slightest... they get warranty claims by the thousands and a bunch of from people tho practically threw their phones into wood chippers and claim that nothing ever happened. They've heard the "I know this looks like I dropped it, but I didn't" story too many times to count.
Sorry to say but I can't see this turning in your favor... everything is working against you here. I'm not sure if it comes across as such, but we here are all on YOUR side... We don't work for Samsung (or at least I don't think anyone here does). We have no financial interest in denying your claim and forcing you to deal with it out of warranty. These things break far too easily and it seems that, for whatever reason, the S7 might be even more brittle than the average phone. But on the other hand, if you just showed me pictures of that phone and the damage, my educated guess would stamp "impact/fall damage, deny warranty claim" on it. I know that's not what you want to hear, of course. But that's the reality of the situation.