The slice of deli meat could have had any number of things in it, including gluten and/or soy, that would not mix well with the other things in your stomach. It could also have carried bacteria your stomach wanted out immediately.

It's pretty hard to tell with the limited info available, but many posts on PH have in common statements that people starting feeling better within a week off grains and sugar AND bad reactions are almost immediate when re-introducing them. YMMV.

I think that's totally possible. I remember getting accidentally glutened in my first GF year and wanting to just die on the bathroom floor. Now, an accidental glutening is not so horrid, because my gut is healed. Our bodies are so much more sensitive than we give them credit for.

Watch out for hidden gluten. It can be such a set back and it's never worth it. You'll get your GF sea legs!

I quit sugar, gluten, grains, and "bad" oils all at the same time, and very soon after became very sensitive to bad oils, and somewhat sensitive to gluten. It only took a few weeks to become sensitive. I think it is very feasible that you are averse to one or more of these things after 12 days.

Regarding lunchmeat, there could be some small amounts of gluten in there, but probably also a lot of salt, preservatives, chemicals, colors, and other things. It might be one of those things setting you off. I now have trouble digesting salami and some other cured meats, even though I didn't intentionally quit eating that. I suspect that my dietary changes decreased my overall level of inflammation, and I am much more sensitive to certain foods and toxins now. In retrospect, it is amazing what I used to put up with and consider normal.

Have you met Mr. Nocebo effect?

Sorry about TMI.

Yes, it's possible to get reactions right after eating the offensive food. Nowadays I have a very healthy gut / bowels, but...

...even when I eat super clean Paleo, once I eat some ice cream or a glass of milk, my guts go completely bonkers. It feels like my intestines go completely liquid and I can feel that liquid furiously swishing inside me. And then I start thinking... Oh God, oh God, oh God... diarrhea!

I don't think it's the milk itself trying to come out my rear end, after all it hasn't even been an hour since I consumed it.

But on topic: gluten.
When I eat gluten (pancakes, bread, whatever, even just a few bites), I feel like I have a heavy brick in my stomach. I have to sit down because my stomach feels so heavy, like an anchor.

I think 12 days is enough to notice the difference. Before, you were under the effects of gluten all the time, you considered them normal so you didn't pay attention to them. But 12 days without? That's enough time to feel the REAL "normal", so once you ingest the gluten, you sure notice it, specially if you are extremely sensitive to gluten.

I'll tell you my experience doing the Gluten Challenge & maybe there's some interpretation to be had from it.

I took 2 months going GF b/c anything less I didn't think was adequate (my opinion). After 2 mos I decided I'd go 2 weeks re-introducing wheat/gluten... w/in the first couple days I felt like I had the worst flu ever! GI distress (in the form of D>), migraines, "foggy head", no energy, bouncing btwn no appetite & ravenous, peripheral neuropathy, extreme joint pain (i'm 30 & felt like i was walking around like I was 80 on SAD), etc...

That convinced me enough that I went GF for a year... then for kicks&giggles thinking maybe I "fixed a wrong" I tried eating a burger w/a bun... the same symptoms as above for 3 days. It's hell. Thoughts of "how to end this physical pain" (mostly GI & joint pain) come to mind... and I can tell when I've been glutened... it all starts w/a migraine, sinus prob's, then for a few days the D> kicks in.

So, it depends on your level of sensitivity. I think it's a smart idea to talk to your Dr. about your concerns & see what they say. If you get Dx as Coeliac, there are programs/assistance you can get to help start you out, inform you, help re: Cost (at least in the US).
Some may be able to do a short elimination diet & know w/in hours/days based on symptoms. If you're just "GI" (intolerant), it may take longer & you're more likely to get a negative result, which then depends on your Dr & what they want to do.

So, that's my story, hope it's helped some way.

Yup, i can definitely tell from my body reaction when something has had gluten in it. Bloated stomach, sluggishness, cramps. It's strange what our bodies can get used to with prolongued exposure. This is probably why it is so hard to explain to a non-celiac what gluten can potentially do to your body.

Offtopic: They stock reduced carb cider at the local bottleshop around the corner. Australia FTW!