iphone deleted text issue

Fairly common problem but perhaps the common solution/s aren't applicable. I accidentally deleted a conversation/thread a few minutes ago. One I really need with lots of information, photos etc. I have a phone that is on another person's account, with my own ID. I don't have anything backed up to a cloud, no itunes, no Mac. We actually had the two phones on the same ID for years with no issues, we each had our own phone numbers, texts/conversations - but recently we started getting one another's texts, and both phones would ring when we received calls, so that's why we set up the second ID. How can I get the deleted conversation back without using the cloud or Itunes. Thank you.