I use messaging all the time, so I understand that sometimes we need messages that have already been sent to us. I welcome the opportunity to help. It's true that once a message has been deleted from the phone, you are not able to retrieve it. However, you are able to download messaging threads, so you can save them. Is this something that you do? Tell me, have you checked any previous backups, to see if the messages you want are there? What is the make and model of your phone? Please share these details, thank you.