Briggfoot:

"from what i understand, Dmixylodian only has the F# anyway as it is the mixylodian of G, which only has the F#.
so howcome it looks like its missing a sharp??"

-- It only looks like it's missing a sharp in reference to a D major scale. D major has two sharps (F# & C#), D mixolydian has one (F#). So if you're looking at a piece of written music that has one sharp in the key signature but the keytone is D rather than G, then you know that it's a D mixolydian tune, since D major has two sharps. Same thing if it's written with the D major key signature but all the C's have natural signs in front of them. Hence my comment about missing a sharp.