All praise is due to Allah, blessings and peace be upon the Messenger of Allah.
Islam has given the husband the right for divorce and the final say to put it into effect or not. Therefore, if a husband is uncertain that he has divorced his wife or not, then she is not divorced as the marriage bond is confirmed with certainty so the situation remains as such unless there is certainty or predominant conjecture, as per the Fiqh maxim: "Certainty is not removed by doubt'. If there is uncertainty on the part of the husband that divorce took place, or he conditioned her divorce on something which he doubted that she did not abide by like when he says to her: ”If you do not do so and so, you are divorced,” then was unsure that she did not obey his command, divorce is not effective.
However, if the uncertainty was on the part of the wife, then divorce does not take place as the final say in this regard is the husband`s.
Al-Khateeb Al Shirbini (may Allah bless his soul) says: “If the husband doubted whether he divorced his wife or not, or that she did not abide by his condition like his saying: If that bird is a raven, you are divorced, but was uncertain that it was or was not :we do not judge that divorce had taken place. Al-Muhamaly said: "this verdict is based on the consensus of Muslim scholars because the religious principle in this case is non-divorce and the continuity of the marriage bond.” {Mughni Al-Mohtaj,vol.4/pp.491}.
The couple in question should fear Allah, The Almighty, and the wife should not deny her husband`s right in having intercourse with her unless she was absolutely sure that divorce had taken place, and Allah Knows Best.