Personally, I'm more inclined to think that a pupa stowed away among materials that ended up at a local nursery (vs foodstuffs arriving at the food terminal). After all, you could have the larvae feeding on weeds growing next to the plant that's actually being transported. Here are some additional thoughts beyond what's in the iNaturalist commentary:
For years, I have been keeping tabs on sightings reported in the mid-Atlantic via Rick Borchelt's LepBlog. Often, Rick's weekly blog provided a useful "heads up" of what we might expect to be heading our way. In all the years I read his blog, I don't think he ever mentioned Dorantes Longtail turning up anywhere in the mid-Atlantic. Unfortunately, he has stopped writing weekly reports as of this year.
If this individual had turned up in the fall, I'd be somewhat less skeptical about it being a legitimate stray. But it has turned up in April, during a brief warm spell (unusual, but not really "crazy weather" in my book). So that's strike number 1. If this had been a Long-Tailed Skipper, and there were other reports of them moving northward this spring, I might have said OK, Long-Tailed Skipper regularly disperses north, and the weather is a little different this spring, so maybe one showed up super early. That would be just barely plausible. But this is Dorantes Longtail - never reported in the fall, when it might be expected - not even in 2012, when the warm weather came a month earlier than this year. So that's 2 strikes.
Look at the condition of the butterfly. It looks perfectly fresh, with both tails intact. Does that look like something that was carried on strong winds all the way from Florida? Strike 3.
Yes, it's possible that it's a legit stray. At the end of the day, does it really matter one way or the other? I don't think it should. I don't think we should make a big deal about the first sighting of a species in Ontario. Maybe if we have another one in the near future (supported by hard evidence like this one), that might be noteworthy.
Here is Rick Borchelt's take on it, sent to me via email:
"Really doubtful. It’s been warm but we have seen zero evidence of anything lifting northward — pierids, other skippers, even Monarchs. And this one is awfully fresh looking for being blown a thousand miles. I think that argues for a transportation event, perhaps from a spring break reveler. "
Rick is based in Maryland, but he gets reports from folks all over the mid-Atlantic. As I said, up until recently, he posted a weekly blog which reported what was being reported from all over the area, along with forecasts of what species were likely to turn up in the coming days.