I'm with you, LB20. Agnok, my impression is that you have a couple days' grace to get that third recommendation in, but you
must submit it to be considered for admission.
If you think your third recommender is going to be a few days late, and there is a good reason for this, you might try calling the admissions office to see what they say. If you think that third recommender is
never going to submit, or will submit too late for you to be considered in Round 2, you might try finding someone else right now who is willing to turn around a recommendation for you quickquickquick -- i.e., in the next day or so. Good luck!