The attractive nuisance doctrine applies to the law of torts in some jurisdictions. It states that a landowner may be held liable for injuries to children trespassing on the land if the injury is caused by an object on the land that is likely to attract children. [Wikipedia]
In my view, the driver is still liable (and that mustn't ever change) but Snapchat should have to prove to a judge that they shouldn't also be found liable.