Each host sends out the bonuses for their individual challenge(s), so the distribution varies. Mid-month seems like a fair amount of time, but real life sometimes gets in the way :) I can help you out if you participated in and didn't receive one for the sketch challenge or desktop challenge. Otherwise, you might PM the challenge host and say pretty please
ETA: also double check to make sure you posted a link to your layout in the challenge forum and not just in the gallery