to have something snatched away from under one's nose
「トンビに油揚げを攫われる」という慣用句は英語では次のように言います。
ーto have something snatched away from under one's nose
例:
My best friend started dating a guy I had a crush on for a long time. I feel like I had him snatched out from under my nose.
「親友が、私がずっと好きだった男性と付き合い始めて、トンビに油揚げを攫われた気分だ」
ご参考まで!