There is a lot of people and a lot on their minds so maybe they just accidentally forgot to call you. Usually if it's that close they usually do, unless you did something to upset them, but most still do regardless.
Now, if you are the one that didn't get call you can do a few things. One, you can show up anyway with the chicken and everything and then they will have to pull you aside, set up a table and ask for forgiveness. Then there are the ones that got called, but they are not happy with the family or the decease or for whatever reason. For these, they usually tie up the legs or take out the lungs. When it comes time to cut the chicken up they'll see these symbols they'll call the person who brought the chicken over, pull up a table for him and ask him what is the problem and ask him for forgiveness.
Me personally, if you have a problem with the decease or family then don't go. If you go, then don't cause anymore problems, the family has enough to worry about.