I just dismissed a troll but realized I wanted to troll them back. I couldn't un-dismiss

I went back to my notifications and clicked on their comment. Nothing. I went to my comment and there wasn't the dialogue box with an X through it for me to click on. I went to their commenting history and clicked on the comment they left and it went to the story but the comment was gone.

Do we have permanent dismissals now? If so, tread carefully. I know I have clicked/tapped the wrong things before but I have always appreciated being able to undo it.