I think similarly. I also have a feeling that many (but probably not all) exotic craft are more like our earth skateboards, so we won’t find any engines on them. I feel in many cases the occupants move these things around with their minds. The craft just forms a protective barrier, and maybe enhances the mind’s function, or something like that.

In any case we need to be careful with our assumptions. Of course we want to find the engine as the first priority, but what if they don’t have and don’t need engines? Who knows.