I think you labeled it correctly, dissociation. If you take a look at the Dissociative Experiences Scale here: Dissociative Experiences Scale (DES-II): Screening for Dissociative Identity Disorder and more , you will see that it is a common experience for some people.

One incident isn't really a reason for alarming concern. Could be a response to a particular distressing event or perhaps an actual/symbolic reminder of something you have dissociated to before. Of course talk about it with your T.