At some point of the dive, it happened to me that I was paying more attention to the camera than to the guide, so I go easy on the pictures, other thing that I blame myself was that my backup lamp is LED and the primary was a normal one that the shop provided us, so I switched in the second dive, but I didn't check that it has no lanyard, and there were places were if it feel, I won't be able to get it back because it was to narrow to get my arm into.
As you, I pride myself on checking my equipment two or three times before a dive, but still have that stupid mistake.
That's one of the things that I think is as challenging and rewarding at the same time of scuba, you keep learning and as time goes by, you realize that still have a lot to learn, and never give thinks for granted