Meng_Tze:
Taking the OP write up at face value.
It seems the guide was too pre-occupied with himself. Losing sight of buddy, going through restriction without checking buddy (he should have noticed there and then that buddy was not around). My debrief would have been straight forward and to the point: '*** were you thinking?'
I can see a lapse of attention in lead tracking buddy. But there is no excuse for a buddy not to notice an 'attention' light signal. This would be ONE lapse (error in judgement), after that no more diving for me with that buddy. Same as breaking gas rules.
And it does not matter if you are in a two man or three man team.
:no
Moving through restrictions often results in a loss of contact which is one reason that cavern and, I think, intro divers aren't supposed to go through restrictions.
It's not necessarily a lack of attention. If the restriction isn't straight or, for whatever reason, the guy in the back doesn't have a strainght shot with his light beam, the beam just doesn't get to where the lead diver can see it. Once his head is in the hole, he just may not be able to see your light.
Even if the lead diver can see your light signal, he might not be able to do anything about it. He might have to pass all the way through the restriction before he can even turn around.
I've had this happen, where I was ready to turn a dive and thought being at a restriction was as good a time as any. My wife slipped in and my "attention" signal only found her feet and not her eyes. This was a perticularly nasty little bugger with a deep silt floor and it takes a little while to get through and do it halfway clean. The result was her waiting on the far side for me to come through (like she should) and me momentarily waiting on the other side hoping she would come back and save me the trouble. The situation resolved itself without issue but I didn't turn to leave the cave without her either.
Our permenant solution was that we decided to stop and pow-wow prior to entering any restriction so that, if anyone in the team didn't want to enter, they had a chance to say so BEFORE anybody was in. It works real well but it isn't something that I remember ever coming up in our cave training or reading about. It was just one of those things that we had to run into and figure out on our own.
Now he should have signaled before dropping down to pick up a $0.05 piece of plastic but there was no lack of awareness on anybody elses part.