乍然离场措手不及
[zhà rán lí chăng cuò shŏu bù jí]
'乍然离场措手不及' describes an abrupt departure ('乍离场') taken by surprise ('猝手不及'), which together suggest an unexpected departure without preparation or warning; being forced into hastily leaving the scene or situation, leaving behind unfinished affairs, possibly implying sudden loss.