In the first place, when in question, the pass is NOT completed.
In the second place, any incomplete ruling trumps a complete ruling. The 'complete' official needs to accede to the 'incomplete' official. But, by the same token, the 'incomplete' official needs to be 100% positive, and not be making a ruling based on circumstantial evidence. He needs to be able to live or die with his ruling. In this case, the R would need to go with incomplete.
Let the play go unless you see something that makes it incomplete. But, if you positively see something that makes it incomplete - hammer it incomplete.