There are several reasons for "rogue" or "sneaker" waves. One is summation of several wave trains, which may not be coming from the same storm system, often thousands of miles away. As we know, waves tend to come in "sets". Several big waves, and then decrease in size. If you get several large waves, all arriving at once, especially in a shoaling or reef area, then you get the "sneaker". In this case there was a warning--that is that the seas were already at" seas about 4-5 feet at 10-12 sec." Then they noted the "incoming tide began to surge". That surge was the precursor of these large waves.
There are also several other types of waves: Some known by their regional names: rissaga (Catalan), milghuba (Maltese), marrobbio (Italian), abiki (Japanese), šćiga (Croatian). are known as meteotsunami or meteorological tsunami--that is Tsunami type waves but caused by meteorological conditions.
There are also the seiche which is a standing wave in an enclosed or partially enclosed body of water. These are usually caused by either the meteorological conditions, minor tsunami, or as in the first case, by summation waves.
In S. Calif, the N. facing beach (toward the main land, with only a 25 mile channel) occasionally have a series of very large waves occur, with no obvious reason. Some have speculated, that they are summation waves, on top of a large ship's wake--or even summation of large ship wakes.
Usually all of these appear to come out of nowhere, but because they are long waveforms, and at sea, they do not break, there is gradual rise and fall of a boat, or the horizon looking from the boat, until they reach shoal water, and then become a breaker.
Certainly a happy story, because an hour in 52 degree water, plus the trauma of the event, may have been fatal. Also the response of the CG to organize a salvage party--sounds like the Coast Guard of old! Glad to hear of that!
Lessons--when there is an unusual surge--be especially aware--and if any question, get out of the shallow area.
Have a hand held, water proof, floating, VhF radio on your person. Have a Personal locator beacon on your person. I noted earlier today, that I had purchased the Standard Horizon HX 870, which has DSC--and once that is triggered it will set off alarms in other boats who have radios, and even if the CG does not receive the distress, the other boats radios will relay the distress, and the CG would then be alerted. Also local rescue may be affected, and especially in cold water, this might mean the difference between life and death. The VHF radio can give a signal, which the Helo can home on, and rescue will be faster.
One book I enjoy is "Oceanography and Seamanship by William G Van Dorn (PhD in Oceanography. This is a book well worth owning if you are a student of the sea!