I need the same thing for buckwheat free products... People with imaginary gluten sensitivities (only a subgroup) are creating more and more real allergy hazards for me.
As far as I can tell, buckwheat is a fairly exotic ingredient even in specialist wheat-free foods. We once bought some buckwheat pasta: never finished the packet. Typical wheat-free pasta is made from rice and maize. I can't think what the justification would be for adding buckwheat as a minor ingredient to something.
My guess: cry wolf syndrome.
Waiters, chefs, etc. only have so much energy and attention they can dedicate to minding food allergies. If people with fake gluten intolerance constantly barrage food workers with (usually clearly nonsense) requests to modify food items or dumb questions that anyone with a real food allergy would already know the answer to, it’s going to sap the ability of food workers to help real allergy patients.
After I was diagnosed I tried eating at restaurants and believing they could be careful enough, and it did not work out. The problem is often contamination of their ingredients - even if something has no gluten ingredients on the label, and even claims to be gluten free, it doesn't mean it's safe for celiacs. Even dried herbs and spices are commonly tainted. So you'd have to find a restaurant that has certified gluten free whole food ingredients for everything, and a complete duplicate kitchen where nothing has ever touched gluten.
You could take a gluten testing kit with you, but that's expensive, inconvenient, impractical, and you still might end up sitting at the table with nothing to eat.
We use rice flour for cakes. Works fine. Most people don't notice anything out of of the ordinary.
We have a genuine wheat-sensitivity in the family, but it's not an allergy and the consequences of accidentally consuming even a large quantity of wheat, though painful and unpleasant, are neither permanent nor life-threatening, as far as we know. We have an accidental-wheat-consumption-event a couple of times a year. Professional medical advice, and it took a long time to get this far, was: here's a brochure on how to run your own experimental exclusion diet; find out what makes you ill then avoid it; goodbye.
You’re correct that rice is a more common substitute than buckwheat in processed foods. However, many gluten free items such as pancake mix contain a blend of different grain and non-grain flours.
As for the exclusion diet, yes, that’s what I used to believe. It is sort of true for non-celiac sensitivities. Celiac is not as simple as that, and neither are non-traditional allergies like eosinophilic esophagitis. I tried for -years- to identify the source of my malaise, and cut out several things that I have an issue with but never found gluten. The reason is that it is almost impossible to cut gluten out to the level a celiac needs to start healing without a very dedicated effort, and even then it takes weeks to respond if you have a bad case and have been eating gluten steadily. Various times I went gluten free, mostly, for 2-3 weeks and didn’t notice anything. I know now I would have had to be strictly gluten free for 2 months.
I strongly recommend medical testing for celiac. Elimination diet will not necessarily detect celiac and then screws up testing.
For eosinophilic esophagitis, there is no choice but to run an elimination diet where you stop eating everything and slowly add foods one by one, because normal allergy testing fails for that condition.
For normal food allergies, of course you should just take an allergy test.
The main symptom was "bloating", and it went away after two weeks of a very exclusive diet: just rice and fried vegetables. Then we reintroduced each ingredient by eating loads of it for 2 days, except that for wheat they recommended eating loads of it for 7 days because the reaction to wheat can be delayed, as you mentioned. However, within 48 hours of reintroducing wheat the symptoms had returned, strongly, so it was fairly clear.
We continued with the rest of diet plan anyway, and a second sensitivity was detected: lactose. Apparently it's not unusual for people to be sensitive to wheat and lactose.
It was quite a fun couple of months, really. We ate loads of things that we'd never tried before. I'd recommend it to anyone who suspects that something in their diet might be making them ill. It broadens one's culinary horizons if nothing else.
For me, the attempts at self diagnosis were long ago, about 10 years back. I tried a wide variety of diets over the years and developed very wide culinary horizons - mainly organic whole foods, and I was a vegetarian for 7 years (I don’t think one would fare well on just rice and vegetables since that lacks much protein...).
My mother had long said the recommended test was to avoid wheat for 3 weeks, then eat some and see what happens. As noted I was not able to find that gluten was the culprit, though I identified various other intolerances. Part of my issue was that I have two separate issues, and esophagus disorders and also celiac, and was trying to find one cause or solution that fit both.