Well, SCOTUS has ummed and erred over several cases about whether to extend the 4th Amend to third party data in some scenarios. IIRC there is an online email case working up through 9th Cir right now?

One of the reasons giving for (usually) now requiring a warrant to open your phone they grab from you is because of the amount of third-party data you can access through it, although IIRC they framed is a regular 4th Amend issue by saying if you had a security camera inside your house the police would be bypassing the warrant requirement by seeing directly into your abode.