Sounds like you really can't be more thorough than you already are, so congrats on that.
What a PITA that mystery glutenings can still happen, but rest assured you're not the only one. I've seen plenty of threads started as a "what of these things could've glutened me" question.
Sometimes a likely culprit is found & sometimes not. One that comes to mind that has surprised ppl is handling pet food w/ gluten - surprising since their suspect list naturally starts exclusively w/ human food & the gluten-detective process doesn't always go back to step one - making a suspect list - after it's been done once.
For some, maybe their top suspect ends up being a trip to the country during wheat harvest or they were somewhere that may've had airborne flour exposure where someone had been baking (it's said to last a day or more) or they find their friend's Pam-type spray was the one w/ wheat flour, though they'd dutifully all 'actual' ingredients.
Anyway, to answer your question, yes it can happen so slyly that ppl don't always figure out how. Hope you're feeling much better asap. Omg how I hated the vertigo pre-gluten-free.
Thank you very much. It took a couple more days for me to feel like myself again, but since then, all has been well. I had wondered about the cat food, but I've been trying to wash my hands after handling it each time. Pesky cat. I may put her on a gluten-free diet, as well.
Yeah, the vertigo was mean. I don't miss it.
Thank you again.