As far as I can recall .. stuff in the lockbox is there because it has been deleted from the main forums. It doesn't necessarily have to be an entire thread, it could be part of a thread, or a post within a thread. So potentially someone who has the ability to delete posts on your forums may have deleted part of that thread you're looking for. That would explain why you're only seeing a partial post and why, when you try to delete it, it still remains (because, in effect, the lockbox IS your deleted post).
I'm not sure why you can't see the actual "live" thread though - obviously I don't have access to your forums, but if GL guys can see that thread you're looking for, then it must still be there .. perhaps it's been moved - accidentally or otherwise - to somewhere you're not expecting it to be? Or perhaps it has been placed in a forum section you don't have access to, for some reason?
I am using firefox, always have, never had this issue, and your right there should be pages at the bottom, but there are none, that is the issue, I get only this page, no going forward, just this page, for some reason it is in the lockbox, not sure why, but that is all I get, I even tried to delete the post but nothing, it is still there. Sorry, but I am running an Asus gaming machine, windows 7 and I have always used Firefox, I hate Explorer, and kept getting errors with it, and lets not even talk about Google Chrome, so I stick with firefox, simple and has worked for me for years.
I've checked again and there must be something very specific to your device or browser that is causing the issue, at least that's the only thing that comes to mind. There's nothing off about that forum thread compared to any other forum thread. At the top and bottom, there is a place too select which page of the thread you are viewing. It should look like this.
Can you let me know what browser/device/resolution you're on? There could be some odd combination of those that's causing certain elements to not show properly.