When you first set up your Securus eMessaging account, you locate your loved one and add them to your contact list. If your loved one gets transferred to a site that does not have two-way eMessaging available, their name will leave your contact list.
If this happens go back to using JPay.com or JPay apps to temporarilly go back to emailing 1-way. When they get another unity tablet, you will see their contact drop on the JPay systems and reappear on Securus.