I've seen clutches fail in 2000 miles. Not on an ST but the point is it depends how you drive. If its spent the past 16 months getting its arse ragged 24/7 or hes been riding the clutch without realising then its hardly surprising its failed!

Personally I'd just buy a clutch and fit it yourself. If Ford strip it and put it down to wear and tear then hes fucked. Even if he says no to fitting a new clutch theres the ridiculous labour to strip, inspect and refit.