Can you ask in an non-suspicious way if they remember something pertaining to that memory? Like say, “Hey! Remember when such and such happened...?”. If they say no, you could just pretend you mixed it up with another thing that happened. OR! Why don’t you secretly write down these memories in a journal... Make two columns of why the memory could be real and why can’t be real. Make sure to put down what age did it happen, the day, the time and see if it adds up or make since. You can share it with your therapist to help you.