This was Jeanette Winterson's pick, Echo, by Carol Ann Duffy.
I think I was searching for treasures or stones
in the clearest of pools
when your face…
when your face like the moon in a well
where I might wish…
might well wish
for the iced fire of your kiss
only on water my lips, where your face…
where your face was reflected lovely,
not really there when I turned
to look behind at the emptying air
the emptying air.