Actually have been present during a rogue wave hitting from astern and washing every item on deck to the superstructure. Viewed the activity from an aux. maneuvering station on the bridge level, during a materials transfer. A solo wave at least three times the average height preceded by an equally deep trough, dropped the stern sufficiently for the wave to top the fencing and ride the deck forward.
An interruption of the evolution had just occurred, and no crew were present in that area, so casualties were avoided. In this type of incident, there are no tattle tale signs before, or remnant changes afterward in the sea conditions. Rogue waves just happen, seemingly at random.
I read an interesting book called “The Wave”. Some gal that was trying to figure out and write about the rouge wave thing. She traveled around to various science places and wrote about them. Theories, modelling, big tanks full of water, etc. After the 3rd or 4th country she was in, one of the science guys said “Well - if you really want to learn about big waves, you should get in touch with these surfers.”
Much of the book was her following surfers around the world in search of the biggest waves.