First dive trip (Cozumel, Oct 2005) after OW, I hogged through my air, being a new diver, and I felt bad about ending someone else's dive, so I did a solo safety stop and then surfaced. No boat! I bobbed around for a while, not having an SMB. I held up my octopus, since it was bright yellow. After about fifteen minutes, I began to feel a little nervous and quickly took stock of my situation: The current was carrying me towards an anchored buoy. Failing that, it was carrying me towards the dock where the cruise ships were moored. If worse came to worse, it was only a half-mile to shore and I could easily make the swim.
Just as I was preparing to make the swim for shore, another boat came along and asked who I was diving with. I gave them the name of the dive op/boat, and they radioed them.
Finally, after I'd been bobbing on the surface for a total of approximately a half hour, they showed up and picked me up.
Apparently, the dive guide for the second team, got to depth and realized he had to crap, so he surfaced, they boogied for land, he dropped a log, and they returned. He was razzed unmercifully for it... LOL
(I now keep an SMB clipped to my BC all the time.)