Other mistake: Charlotte's dad buys a newspaper in the beginning of the film. The same two paragraphs about Prince Naveen are repeated all over the front page, including under the headline 'Annual Goosenhoper State Gumbo Faire Is Smashing Success.' (00:08:45)
Other mistake: When the old woman is cooking gumbo in a large bathtub, it's shown boiling and really hot. Yet the two frogs can sit right on the rim of the bathtub inches above the boiling food in a non insulated tub without getting burned or even hot.
Answer: They physically left. Just because we didn't see it happen doesn't mean it didn't happen. It's a montage of their activities after they returned to human form.
LorgSkyegon
I thought as much, but it would have been even better to see a montage of them physically leaving the bayou and planning their church wedding.