Typically a flashing engine light under those conditions indicates a cylinder misfire event. The flashing light also means that whatever is occurring may be bad and you should stop doing whatever is causing it....in this case if it only happens at WOT you should stop being at WOT if the light starts flashing. I also wouldn't immediately freak out and suspect the engine is getting ready to blow either. In my years of working on cars a cylinder misfire is a very, very common condition and could be as simple as a bad plug, coil, injector, or even a bad tank of gas. Sure, it could indicate a more serious engine issue is starting to happen but always start with the simple things first.
The engine light does not have to be actually on at the time see any old codes, however a cheapo base model code scanner may not be able to see stored codes. The codes stored in the ECM just do not randomly disappear, but will go from active (i.e. engine light on) to stored or historic status that you should be able to view until cleared with a scanner.
In any case, if it happens again and you can see a code I would suspect it will give you a misfire at a specific cylinder. The first thing I would do is a visual inspection of that cylinder and check the connections. The next thing you can do is swapping parts between cylinders (only do 1 at a time!) and see if the misfire follows the part or stays with the cylinder. For example if there is a misfire on cylinder 3 swap the plugs between cylinders 3 and 5 and go drive. If the misfire is now at cylinder 5 you know it's probably the plugs. If the misfire stays at cylinder 3 there is something else wrong. You can swap the coils and injectors around next.
