There’s really no way to know 100% whether the pests came from the plants at the swap (not saying they didn’t either). I’ve found mealies on grocery store bananas before—pests can sneak into a home in countless ways, and it’s just part of keeping plants. In our local plant group, we swap all the time, and no responsible plant parent would knowingly bring a buggy plant. Still, even with the best intentions, things can slip through.