1. Click the "Save" link underneath the Title of the thread. This will add the thread to your "Saved" list which is accessible via the dropdown menu invoked by clicking on your username in the upper right-hand corner.
2. If you add a comment to the thread, your comment will be saved in your "Comments" list also accessible from the same dropdown.
Does it never recognize you [no, you're here now], or just it just take a bit to recognize you? I would guess the latter. It sometimes takes a couple of minutes or so to recognize me - the joys and surprises of internet traffic!
You've got a couple of options...
1. Click the "Save" link underneath the Title of the thread. This will add the thread to your "Saved" list which is accessible via the dropdown menu invoked by clicking on your username in the upper right-hand corner.
2. If you add a comment to the thread, your comment will be saved in your "Comments" list also accessible from the same dropdown.
Does this suffice?