Hi ARM -
I completely understand your frustration! The way reflux seems to defy explanation fits your description. I encourage you to keep searching, though. IMO, diets like the one you mention don't go far enough for many folks. Instead of looking at individual foods...maybe what you need to consider are ingredients, like these:
gluten
dairy
eggs
corn
soy
sugar, fructose, or artificial/sweeteners
MSG and hydrolyzed vegetable protein
Another helpful thing to weigh together with this are other chronic symptoms. Headache, sinusitis/PND, joint pain, const/diarr, hives/rashes, depression (not just from dealing with this stupid condition!), anxiety, excess gas, etc.
This can get complicated, so don't try to rely on your memory of what you ate yesterday, or the day before. Approach this methodically with an elimination diet, and even a food journal. Like i said, instead of thinking "carbs," "tomato sauce," or "chocolate," for example, narrow your focus.
What makes following this trail challenging, is that there is not always an immediate correlation to symptoms. Immediate reactions can fall within a 12-72 hour window, and the half-life of some of these ingredients can last for nearly 30 days in our systems.
Sometimes GERD is just unexplainable. But you may be fortunate and finally discover something important. Keep trying!
-Bruce