Did you delete the text message thread or have the phone set to delete old text conversation threads automatically?
As for getting them back, you should have a backup app installed that can save both SMS and MMS messages to be able to restore the items. Yos can get one from the Play Store. It would have needed to be installed prior and scheduled to run the backup before the messages were delete. So no you won't propably be able to restore the messages now.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
