I think exactly one second after leaving your car, it starts heading toward any bit of poop or carrion in the area. You ever-so-slightly increased the genetic diversity of the fly population.

I very much doubt that a fly much cares for the geographic location of the pile of dung it munches on and lays its eggs in.

By the law of averages another fly has hitched a lift the other way and so the balance of the universe is restored.

I’ve kind of wondered this too, more with spiders than with flies. I escort spiders out the door when I can, recognizing that I’m transporting them away from their neighborhood. It’s up to them to work it out.

Flies are pretty repugnant, but spiders can have some personality and grace. And they don’t buzz.

Quick googling gives a lifespan of 28 days for a male housefly and an average speed of 5 mph. But I wouldn’t hold out much hope for their memory. By the time your hitchhiker gets home, nobody will remember him. He might as well stick around wherever he landed and see what their food supply looks like. That’s probably more important to him (along with the fresh crop of lady flies) than hanging out and reminiscing with the old gang.

Oh, the page I read also said flies may travel as much as 13 miles from their point of origin. For all you know, you were taking him home.

Oh! Well…umm…never mind. I thought it said files.