Cannot Add Removed Conversation

I added a conversation with someone and they didn’t end up receiving my messages. Then, they tried sending me one instead and it worked, but it created a duplicate conversation. So, I deleted the original one and it deleted both conversations.

After this, I could not re-create the conversation and, thus, cannot contact them. I was able to create a second account and message them, but I would prefer to keep my original user name. Is there anything I can do (other than report the bug on Gitlab)?