I don't think there **is* a term to describe a descant that's played rather than sung.
You could call a descant a type of counter-melody - "a sequence of notes, perceived as a melody, written to be played simultaneously with a more prominent lead melody." But unlike a counter-melody it's always pitched above the melody, and is restricted in having to accommodate the same number of syllables as the melody itself. And, because we mostly encounter descants in hymn-singing, they've got a reputation for being glorious. Counter-melodies generally manage to avoid that!
So when such a thing appears in "classical" music - and I'm struggling to think of an example, though they're surely common enough - it would probably be described as "a descant-like counter-melody."
That'd be a rather academic way to describe what the trumpeter's doing in that Shakira song! He/she could just be improvising it. But that's how the Whole Thing started a thousand years ago: with monks improvising counter-melodies to the plainchants!