Fingers crossed
Pray for good fortune or good luck.
祈福，求好运
e.g. I reported to the police about my missing wallet. They promised to investigate, but warned me not to keep my hope up. Anyway, my fingers are crossed.
我去警察局报案丢失了钱包。他们保证会去调查，但是提醒我别抱太大期望。尽管如此，我仍祈祷（钱包能找回来）。
