【翻译】我本来以为你走了，没想到你还在！

I thought you had left, but you are still here.

注意，thought 在这里有“原以为”的意思。
本人翻译仅供参考。

I thought that you had left,I didn't expect that you are still here.

I thought your were gone.But actually you are still here!

i thought you just left, but you are still here!