Just to add a fuller picture to all this:
If everything was in place at 2:30, we must have disturbed the thiefs on our entry just about then.
As we were laddering the pitch into the main streamway, there was a light approaching along the traverse, he/they then turned and went back up the streamway, followed by a very loud crash (like a heavy tackle bag being thrown?).
As we went upstream, we noticed the second section of rope hanging just above head height, and higher up a rope in the water. I assumed it was in the process of being rigged.
At the master junction we met a bloke and I actually asked him if he'd been messing with the traverse rope (thinking I could ask him why he was rigging it), he was unable to answer, thinking he hadn't heard me I asked him again, he still couldn't answer. Then his mate arrived who was more talkative, said they'd just come down Swinsto (in which case who'd been on the traverse?).
This is exactly where we found the 3 krabs on our way back. Fortunately, we didn't catch them up otherwise I'd have returned the 3 krabs to them!!!
Could be a coincidence, if only I'd know earlier that Slug had previously rigged the traverse!
I spoke briefly to an ULSA girl as she reached the head of the pitch and we exited, there was no-one outside.
Seems a funny time of day (busy Sunday afternoon) to rob a cave, unless it was just in passing.