The most simple and effective way to let somebody know you meant to not talk to them, call on their birthday, acknowledge them in public or admit to yourself you know them. To go against the grain of all the people who contribute to their sphere of attention and attention seeking and their self image of a good, upstanding person or whatever the fuck their concern is with the public eye watching.
Don't ignore me I'm scared I won't be around one day and nobody will give a fuck what if they all end up celebrating me not being around anymore awwww how horrible.
Something people will claim to do with the actual intent of NOT ignoring anyone; they just want to leave a conversation but want an excuse as to why they've stopped responding. However they never actually ignore the person because they still want to see what he or she is saying about them.