If you did find out their carrier, you could use the SMS gateway. What this would do would allow you to send an email and they would receive it as an SMS, and when they reply, they would reply as an SMS message and you would receive it as an email.
This should bypass any of Verizon's agreements or lack thereof. The only downfall of this would be knowing their carrier. Once you do, you could add that address into the contact's info and you're good to go. Email to SMS Gateways, Complete List | mutube