Here's what happened:
There was a bit of a backup on a par 3, and we pulled up behind the previous group before they hit, and waited in our carts while they teed off. The green complex isn't visible from where we sat so we didn't see the results of any of their shots. After they drove off, we walked out onto the tee to get ready. The right half of the green has water in front and while we were there waiting, it was apparent that one of the guys in front of us, based on where they were all looking, just didn't quite clear the hazard. After looking for a few minutes, and all three of them discussed it, he dropped just to the left of the hazard at that point. We found that odd, because it's not a shaved bank or a steep bank, so it seemed unlikely to us that it would have carried over the hazard and then fallen back in. But we also didn't see the shot, and it's not our group, and he certainly consulted with his two other group members before continuing.
We just shrugged our shoulders and let it go. Should we have done more? Should we have yelled at him then, or confronted him after the fact, or a third thing? Just curious.