When you tried setting up the phone, did it tell you it was locked by Verizon? Typically Verizon will automatically unlock their phones after 60-days from the date purchased. The only exception that I am aware of is when a phone has been reported lost or stolen.

So yeah, Verizon should have be able to provide that information. At the very least, Apple should have been able to tell you the date it was activated as well since it would have also recorded that as the support and coverage eligabilitiy date.

Reference: https://checkcoverage.apple.com/