Sounds like a pocket of memory has burst. Yes, this did happen to me. I have a generally non-functional memory. I often can't remember yesterday. It makes it hard to function.
So when suddenly a very distant memory becomes so real and distinct, it's almost more like a flashback than a memory because it was sealed off and unrehearsed for so very long. This kind of thing doesn't happen to me outside of child memories near the trauma time.
My hypothesis is that all the memories that are stored near the trauma memories (on the timeline and maybe in the same area of the body and/or brain) get sealed off by dissociation along with the trauma, even if they are non-traumatic.
My friend, who got hit by a car, has no memory of the 2 weeks after the accident, during which he supposedly was talking, eating and acting normal in hospital. But to him, there is no recall of that time after the brief coma. Those memories, eating and drinking and talking, were not traumatic, but they got dissociated along with the trauma.
I'm very sorry and sad to know that other people were also abused by their own dad. It is heart-breaking to me.
This sounds like a sign of healing and integration. I wish the best recovery for you, and to not push to hard to remember. Loving yourself and unconditional self-acceptance is the 100% lesson at any stage of healing, regardless of what is or isn't remembered.