Remaining nodes?

One of the recent questions and answers(someone else's, not mine)  did not completely answer my question.  The writer had chemo.BEFORE mastectomy.  
I had mastectomy, THEN  8 chemos, now will start radiation soon.
15 auxillary nodes removed with mastectomy---14 positive.  How can I know that more positive ones do not remain?  Is it likely or not?  All scans and tests after mastectomy were clear.
Are the nodes lined up so that if one finds the last one negative, does that mean that the cancer has not gone on to the one after the negative one?

[CCF-RN,MSN-rf]

Dear seven7:  In general, surgeons remove a layer of lymph nodes that is in the "fat pad."  This number varies from person to person.  Regardless of outcome, the doctors do not remove all the lymph nodes - some are needed to minimize the risk of lymphedema.  Although it is logical that lymph nodes would go in order, there is no guarantee that all lymph nodes containing cancer cells have been removed.  Thus, the reason for chemotherapy.  Theoretically, there is less bulk of disease if there is any left and the chemotherapy and radiation therapy will hopefully take care of it if it exists.  The other person's pre-operative chemo was a different situation and should not be compared.