Just wondering how your lo is doing now?
Have you tried any more squash? only reason I ask is because my dd has something called FPIES and it's a food intolerance - a common trigger is squash (but mostly winter squash - I think you said it was summer squash) but any food can really trigger it.
Your description sounded just like what happens to my lo - right down the the doc saying it was a GI bug
Although it's *just* an intolerance, it requires emergency medical intervention as it is life-threatening.
And the reactions are delayed - but usually more like 4-6 hours later after the food is eaten, and most often it will happen on the 3rd or 4th exposure to a food, too - not on the first. So it's tricky to figure out what is going on.
Hope that's not what it is, but wanted to mention it just incase you try the squash again and the same thing happens - most doctors are not really familiar with it - it took us 2 trips to the ER, a week stay at CHOP and 3 months of waiting to get a diagnosis!! (which, by the way, we only got because I googled "squash and vomiting" or something ridiculous like that and stumbled across it!)
Hope your lo is doing much better!!