The oversight problem

The oversight problem. If you found on a plane that the stewarding staff have not given you lunch after all the other passengers have received their lunches you will usually find no problem in raising this with them. Now if a friend or work colleague doesn't mention something to you. Are you supposed to raise it with them and perhaps place them in a awkward situation or leave it be and let them remember it in their own time or if they don't take the inference that the forgetfulness was intended? Or you're due to get a ticket for an social event in the post, but it never comes would you contact the host?