Duncan, that may explain why I only got a B- in that course.*
(Yep,
Sappho used short syllables sometimes in that position. But line-ending syllables in many classical meters are generally reckoned "long by position" even if they are short, so I don't know if that would be considered a true anceps.)
* Kidding--I got a B- in that course for other reasons, and I think the professor was being very generous.