What preposition should I use in the following "left X _ Y" construction?

In the following sentence, the person didn’t finish his food:

He left some ham and cucumbers __ the potato salad.

I thought of using "in," but that would be ambiguous; it could also mean that he put ham and cucumbers in the potato salad (or maybe I’m wrong?).

Is "from" the correct choice? Or another preposition?