Nà rén tuìyǐn duō nián, péngyǒu men shuō zhǐ zài cǐ shān zhōng.
That person retired years ago; friends just say 'he's somewhere in the mountains.'
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From 贾岛 Jia Dao (Tang) 《寻隐者不遇》: 只在此山中,云深不知处 — 'he's just somewhere in this mountain; the clouds are deep, I don't know where.' The child replies to the poet who came looking for the hermit master.
usage
Almost always quoted with 云深不知处. The tiny 20-character poem is one of the most-recited Tang poems; both halves have become proverbial for 'close but unreachable.'