If the what the member has stated is true, I think this has to be seen as a very harsh lesson for them to have learned. In the end, if you end up paying twice for the same weekly signature payment then it will mean others can follow suit and claim the same thing. The best thing for the member to do would be to accept their loss and move on.

If they are promoting a service they should at least understand how it functions. You have not done anything to contribute to his loss therefore you should not be making any subsequent payment to him to cover his losses. After all, there is absolutely no way to know whether he is telling the truth or not and if that could be ascertained beyond doubt, you should not be paying signature campaign participants to cover the losses they incurred because of either their negligence or lack of understanding about the service they chose to promote.