Messages with one single person have disappeared

It looks like anything prior to a couple weeks ago with one particular friend has been deleted from all of iCloud, it's not on my phone or on my computer when I load up either one. I am able to load other peoples messages prior to this time, I automatically back up on iCloud, and keep messages forever, and even keep voice files forever. I don't want to lose that information, as a lot of it is work related. What can I do to recover this?

Thanks for any help you can provide.