Lost entire iPhone XR text history with one contact before a specific time last night

I have an iPhone XR, running iOS version 17.4.1. 3 weeks ago, I hired someone and we have been exchanging messages, photos and some videos for my project. We were texting for about 20 minutes last night, and this morning I tried to go into the text chain to review the instructions I was given for the next project phase. Everything is gone before 9pm. GONE. I have no idea what happened.

I've tried turning my phone on and off, turning airplane mode on an off, the Messenger app on and off, but nothing has fixed it. From text conversation page in Messages, I clicked on Edit and Show Recently Deleted, but the only things I've deleted are random political spam messages.

In the Messages app, message history is already set to "Keep Message Forever". In Settings --> Apple User ID --> iPhone XR, iCloud Backup is set to On.

I can't understand why all messages disappeared before a set time last night, and I don't see how to get them back. Any advice would be GREATLY appreciated. Thank you.

[Re-Titled by Moderator]