Thought I'd give an update on this.
After about a month, DS' reflux that was triggered by this event finally settled down. I was giving him pepcid 2x a day, took him to the pediatrician who recommended we try another type of reflux med, and just as I bought it, reflux went away.
During this whole time, we've been avoiding potatoes in all forms, since I questioned them a week after the reaction when he was still eating them and his stomach wouldn't settle.
Once DS' stomach was settled, he wanted to try potatoes again, which I thought was a good idea. It couldn't possibly be potatoes right?! He ate 5 fries, and boom! It started up again. Luckily it wasn't an epipen moment, but his throat felt "clogged", he was burping, had reflux, and was uncomfortable. After he went to the bathroom, his throat unclogged (sorry if tmi). At that point he decided to tell me his throat was better even though he initially didn't tell me it was bothering him.
Reflux flared again for a few days afterwards, and has now settled down.
So bizarre. With this crazy round of latest recalls...the thought crossed my mind...could there be some kind of contamination between potato and peanut crops?? But then I realized that if there were, many others would be experiencing problems. So it must just be something weird with potatoes and him. We've tried all forms. All bad.
We have a GI appt today, and will go to Mt. Sinai in a few weeks. I've been in touch with them by phone, and they were scratching their heads over potatoes as the potential trigger...but all signs seem to point to that now.