How to track sharing on social networks?

Question

Facebook

We have a promo site on the one hand, which is interested in the social activity of users. For each social action, the user is awarded points, which in the end he can exchange for prizes.
On the other hand, a user who is interested in prizes and can share n-th number of pages in his social network account. But it is highly likely that the user will remove the sharing from the social network in a few seconds after the points are awarded. Friends, I need your advice on how to do better in this case. There is an idea to assign an individual id to the user, which will appear in the url when sharing, and, for example, before exchanging points for a prize, somehow double-check the correspondence between the number of points and social actions. But this solution does not seem to me successful either: it is not clear how to automate such a check.
Friends, I hope for your help, thank you very much in advance!