Well. Neither of my two geckos ever did that. But an old friend of mine had her gecko over at my place once, and which she was out roaming a bit on the blankets she pooped.
my one male HATES being handled. and after 5-10 minutes of taking being handled he pees and poops. its his way of saying enough. haha he's a brat but i still love him.
I think it's a put me back sign, but I don't have enough experience to know for sure. I know it has happened to me when I first got my geckos, but not so much now.
My gecko has pooped on me twice, both times when she was chillin' on my leg. I know it doesn't mean that she wants to be put back because when she was on my leg she was basking, absorbing my body heat when she got up, pooped, and moved to lay back down. I actually think that it's more in line with a sign that she's comfortable being around me. It's not really very comfortable for ME, but still.