Getting data from extendTrace

Hello Guys,
can somebody explain me how the Data of extendTrace is stored ?
i made myself a function with d3 Events to create points if i clicked somewhere on my Plot.
This created point will be shown with extendTraces. Now i want to go further and delete this point if i click again on it, but therefore i need to check if this one already exists.
So does extrendTraces stores it somehow in an Array ? is the data stored in the trace i’ve created with newPlot ?
i hope u can understand my question.