iMessage Recovery

I had accidentally deleted a conversation over iMessage that contained important information. My iMessage is backed up over iCloud, my data was backed up before said accidental deletion.

I looked up how to recover my messages online and on this website, and the main consensus was to backup my phone, then reset by erasing all content and settings, and then restoring back to a previous back up date.

I did this, and reset to a previous backup, which would have contained the messages.

The messages were not recovered.

Is there anything I can do to recover them?

If it helps, I have exchanged new messages with the same contact after the old messages were deleted.