No, no, no it's not a bug. The source of the issue is not yet confirmed, we will create an investigation ticket that we will put in our backlog and will review in next sprint planning. Based on our capacity. On investigation results we will see what will be our next actions... :D
Stop pretending that you don't do cowboy style development. Everyone knows how things get prioritised. Also, prod bugs don't go in backlog, prod bugs get fixed. Every team has time set aside in sprint for prod bugs. (Also, who does sprints any more?)