If they’re on the planet I think they’re most likely in the ocean or on the poles. However, being on or in our moon makes more sense.
It’s a big universe, if life is possible on a given place, it tends to happen.
Considering the age of our galaxy, I’d say we have company. Perhaps we’re a transplanted life that has evolved. Possibilities are numerous. But, I don’t think we’re alone nor are we the brightest bulb in the box.