I used a combination of Wikipedia, Latdict, and GoogleTranslate to come up with this:
Nat: "Sum placuit occursum tibi. Quam fugae?"
Stiles: "Mea fuga erat comosus."
Nat *raising an eyebrow*: "Your flight was 'leafy'?"
Stiles *grumbling*: "Latina est linguam stulta, usquam."
What it's supposed to say:
Nat: "I'm pleased to meet you. How was your flight?"
Stiles: "My flight was leafy."
Nat (in English, raising an eyebrow): "Your flight was 'leafy'?"
Stiles *grumbling*: "Latin is a stupid language, anyway."
The idea is that Stiles was thinking of 'commodus' ("comfortable, agreeable") but ended up saying 'comosus' ("hairy or leafy") instead. With the exception of the intentional error, is this correct?