I'm a little confused about the way the group got separated and I'm wondering if the Japanese press might shed some light.
The beginning of this thread described that 6 of the 7 had surfaced and drifted together having been separated from one diver on the first day. However, the interview of the rescued dive leader Saori informs that she left the group on Saturday morning to try to get attention from a passing tugboat, was unsuccessful and also unable to rejoin the rest of the divers.
If the report above is correct, then all 7 of them must have been together after the dive and spent the first night (Friday) together.
I'd say the report/interview above is what I would trust most at this point, as that's from interviews with the divers. I am not sure if she was the dive leader though, as it was two guides and five guests.
IMHO, with good buoyancy control you don't really need gloves with diving in most areas that part of the world. You could just carry a reef hook for those unexpected situations, but mostly just learn to drift and enjoy that as part of the dive.
If I have to climb up a rock in choppy waters, like these divers had, I don't think good buoyancy control or knowing how to drift helps. And "in an emergency situation", which I was saying, there is nothing to enjoy. Holding onto something because someone wants to look at something or bumping into the ground because of bad buoyancy is not an emergency situation in my book.
A reef hook might have helped them in order not get pulled back into the sea, but I have never used one, never hold one, so I don't know how feasible that would be.
Have you got a photo of the size of the container?
I got this one: Custom Divers Dive Canister
You can read more about size and fit here: Scuba diver's Personal Locator Beacon - how never to be lost at sea