If someone makes divorce conditional upon something, such as if he says: “If you visit So-and-so, then you are divorced,” then divorce takes place when the condition stipulated is fulfilled, according to the view of the majority of fuqaha’.
Some of the scholars are of the view that if he intended thereby to threaten her, urge her to do something or prevent her from doing something, then it comes under the heading of an oath (yameen), for which expiation (kafaarah) is required. This is the view favoured by Shaykh al-Islam Ibn Taymiyah and a number of other scholars, and it is the basis for fatwas on this website.
Based on that, if your husband said that he did not remember the action stipulated, but he did not intend to issue a divorce – rather he merely intended to prevent you from doing something – then he should offer expiation for his oath, so as to be on the safe side.
If he says that he did intend to issue a divorce, but he forgot what the condition was, then there is no blame on you for doing whatever you want of permissible things, and no divorce will take place, because the basic principle is that the marriage remains valid, and no divorce occurs when there is doubt.
Al-Majd Ibn Taymiyah (may Allah have mercy on him) said in al-Muharrar (2/60): If there is any doubt concerning divorce or the conditions stipulated for it to occur, then what matters is the certainty that the marriage remains valid. End quote.
al-Baghawi (may Allah have mercy on him) said in at-Tahdheeb (6/104): If a man is uncertain as to whether he has actually divorced his wife, he should assume that it has not happened, because the basic principle is that the marriage remains valid. The same applies if he is uncertain about the number of divorces: he should assume that it is the lower number, because that is what is certain. End quote.
And Allah knows best.