Your anxiety could cause you to be unavailable to him for problems that will inevitably arise throughout childhood. And he could reflect your anxiety by refraining from asking for your help when he needs it. Over time, a pattern of lying and deception could develop from your fears, if your anxiety overrides your ability to separate your anxiety about your ex-spouse from your experience of your son. I am merely playing out the potential for your consideration. Become curious about the meaning of your son's behavior.
Children express feelings through play.
It is possible that he has feelings coming up about his father at this time, and this might be an opportunity to address them, rather than to be afraid of these issues. Feelings about his Dad will no doubt surface at some point and helping him to resolve them will be a natural part of his development. Consider also, the possibility that his behavior was more investigative in nature. His behavior could represent an early interest in science or even art, though it would be too early to know for sure. Consider, too that he may not have interpreted the house rules to include that he could not experiment with that which was his.