Hi Alex, it was myself and my friend you talked to at the crag on Friday. After you left (I hope you enjoyed Upper tor) we did another route and I spent several hours cleaning up the wall to the right of Flash Wall after my partner had to leave (The Thieves Kitchen (E2 5c). During this process I walked round to the top of the crag several times via a short scramble just to the left of the HVS you decided against doing. Unfortunately I didn't see the abseil station you offered us to use after we did Flash Wall but if I go up again soon to do the route I cleaned I'll make more of an effort to look.
The crag is close to the path just above flash wall so if any of the gear was in view it is possible that it could have been taken by a walker thinking it was abandoned, I had something similar happen years ago whilst climbing at Curbar. Another possibility is that unfortunately some people are not a honest as you would hope and could have taken it intentionally if it was visible. Recently whilst at the bottom of the Pagoda (also on kinder) my partner heard a man at the top say something like "look climbers" and then over heard him telling his kids nick/take our belay which I had installed temporarily on the top speed up doing multiple routes. Luckily my partners shouting meant they ran away and dropped my gear on the floor after removing a nut and screw gate and compromising part of the belay which they were fully intending to steal.