I need some help figuring out this meteorological phenomena?

So there is some ground fog here at work (air traffic control tower). I know what makes fog occur, the temperature inversion (the warmer layer of air over the colder layer). But I’m having trouble figuring out exactly why. It rained a little today, but the clouds are gone. You can see the definite layer of warmer air, which means the level of air cold enough to condense water vapor is very thin. I think I’m maybe just having a brain fart, maybe someone can help me turn the light bulb back on.

Is it the rain evaporating back up into the atmosphere, but being condensed to mist closer to the ground because of the warm air above it? And how did that warmer air get above the colder air (or vice versa)?