Just guessing after a short google maps analysis inspired of the picture. (never been to St Moritz area unfortunately) Somewhere close to lej da l'ova? ;-) Pretty sure It's somewhere below the Piz Rosatsch?!
It's called the Hahnensee trail. The Corvatsch gondola takes you up on their first ride in the morning and the last 2 in the evening ... :-) See you on the trails!
naaa....really disappointed that you aren't in the final..anyway, i leave near Swiss border and i know engadina and his beautiful landscape but your picture is really off the record...amazing!