倒裝了，順過來是

This autumn night happens to find me thinking of you.  :)

有“恰巧/偶然”的意思： to discover someone or something/yourself doing something or in a particular situation, especially when this is unexpected。

第三句也是倒裝的，應該是 Pine cones can be heard falling in deserted mountains.

都是押韻弄的。 ：）