I accidentally hid a message. How do I undo it?

I think If you message that person again it'll show the entire convo again

I don't remember her name is the problem. I did it all too fast :( @autumnsmomma125

Oh.. umm ask preggie maybe? @preggie_help_ios

I asked and got no response. @autumnsmomma125

I found her. thank you for your help. @autumnsmomma125