I wouldn't worry about it. Stuff like that happens all the time. If we threw out all food that ever had the tiniest bit of contact with insects, we'd be throwing out most of what we are now eating. If something had been out all day and 50 flies had got at it, I might think about throwing it out. One second's worth of contact with a fruit fly is nothing.

I know it feels gross in your head, but any bacteria left by the fly will be killed during the baking process. That's why it's risky to eat raw eggs, but not cooked eggs.

That's no problem..

i was making a pie and i was mixing the batter in a bowl. i turn my head to go grab a spoon and i notice the tiniest little fruit fly flew out of the bowl. i have no idea which part of the batter it touched. i dont have time to go to the store and buy new ingredients because my guests are coming in about 10 to 15 minutes. I guess my only choice is to just throw it out?