Billy dies soon after the end of the filmHe's seen drinking directly from a stream while telling the Kirbys that Grant was probably headed for the coast. Anyone with even relatively little survival skills knows that this is the best way to kill yourself in the wild, and he almost definitely got sick on the way home or upon arrival. The massive amount of injuries he sustained almost certainly didn't help his condition.
Nash's Satellite Phone was Made of Indestructium and had nuclear batteriesKeep in mind: The Spinosaurus ate Nash, he chewed him, then he digested him. When they found the phone in a pile of poo, keep in mind that Nash bones weren't seen: A Phone, which is supposely made of plastic, and a few pieces of metal and silicium, endures the bites, the acids and antiacids better than BONES. Also, I don't know yours, but my cell phone battery doesn't last for a lot of time, mostly if it's reiciving calls, and has a loud ringtone. The only explanation is, efectively, that it's really Made Of Indestructium.