Many of us on here see theatre more frequently than most. Thereby, making it hard for some to remember if they saw something or not. For me, at times, it’s not that I forgot if I saw a show or not. It’s sometimes my takeaway of a show as in did I like it or not. It get saturated due to me going to/working shows with such frequency.
But, it can also just be time. For example, my brother was studying in London for a years. He had dinner one night with a close childhood friend of my father’s. Lives is Israel but back then, flew to London and NYC for work with some frequency. He said to my brother that when me and my family came into town that we had to see Blood Brothers. He spoke very highly of it. So, during our visit, we did. At intermission, my parents turned to one another and had the same feeling that they may have seen this one before years ago but wasn’t sure. We got back to the hotel and I did a google search to discover that yes, the most likely did see it before during its short Broadway run.