The researchers will have to have gone through some kind of third party agency to get the partecipants. This agency should be queried to see the number they report
What is the difference (to a layperson) between cherry-picking participants and rejecting participants because they do not meet your study's criteria?
Who funds this agency?
Do the members of the reviewing agency have their own biases, and might those biases tarnish the reputation of a study that is actually well-conducted? (hint: this already happens in journals)