You know I would definitely keep those ingredient lists. I think it's a good idea to have a file somewhere where you can just toss these things in and even better attach them to a slip of paper with the date and any symptoms and that way you can get a much better idea of what the problem really is, sometimes it can be surprising and something simple that you might not ever catch if you don't have this info to refer back to.
For me so far I'm finding flour seems to be an issue for me, I get all those symptoms -reflux, pain, bloating, lethargy, along with dysphagia- whenever I eat any flour it seems. I even recently had some rice pasta and am still feeling pretty miserable from it. It's odd but I seem to experience increased sensitivity to other foods for awhile after having any flour product. I used to think it was just wheat, but then I kept adding things to the list and feeling puzzled, but once I finally stopped all flours after many months I found I could go back to eating oats and even things like bulgar and manna bread without any issue. I've even had products made from flour that will cause issue for me while the same thing won't be a problem made from the mashed whole food (things like soy milk, hummus).