Ladies: What does this "signal" mean, exactly?

Twice I’ve had this happen with women who are taken and who know that I know that they’re taken. It’s when I grab something (a doorknob in one case and a camera in the other) and the woman puts her hand on my hand a split second later as if she is “late” to grab the thing that I’m grabbing and accidentally on purpose puts her hand on my hand instead. Is this a come on? Is a reasonably reciprocating response to take her hand? Or something else? It’s weird being in that situation and not knowing exactly what to do.