Ideas that get lost in my mind.

[Eskimo]

Personnaly , when I got a melody that I dont want to forget in my head, I take out my cellphone and I record the sound by humming the melody with my mouth. When later I get on FL Studio, I take out my phone and listen to it again, it worked pretty much all the time.
(By the way if your in a public place (Like a restaurant), try to find a place where there's fewer people, unless you want to look like a retard that doing weird sound looking at his cellphone (Y).)

Well, just start whistling it for say 8 bars, take out your phone discretely, push the record and you don't even have to move it closer to your face, you get the melody down and people will think you're checking the time or a message like a baws