I see two posts on TA, one saying it was simply closed during their visit, and another disgruntled one saying it's permanently closed. I have a hard time trusting anything posted on TA to begin with, and even though I personally don't care for staying at the HRH (in other words, I felt disgruntled after staying there, LOL), I find it unlikely that the slide is permanently closed. (it's the only good thing about the place in MY own personal opinion)
I bet HRH could be called directly to find out about the slide.