Allo Phil
Does your browser have 'tabbed' browsing? If so, instead of clicking on the 'CP' button, try right-clicking and selecting 'Open in new tab' instead. That will leave your original thread still there.
Or, if you look just above the 1st post, at the right-hand side - You should see a button marked 'Thread Tools'. Clicking on that will show a little drop-down menu, an option being to 'Subscribe to this thread'.