Ok, are you saying you don't see the reply when you open the actual thread? Or are you saying you don't see her username (Joni S) listed as the last person to reply to that thread when you're viewing the subforum?
Hope that question makes sense.
I see it fine in the thread, but no it isn't showing when I view the list of topics in the subforum. As I said before, I really think it was just a one-time glitch. I've seen this happen countless times though I'm not techie enough to explain how it happens.

Anyway, there's really nothing we can do on our end to fix it.