Your "availability heuristic " is rather a simple notion.
The availability heuristic operates on the belief that if something can be readily recalled compared to other facts in your memory bank it simply is more important to you than those others that are not easily recalled. It goes hand in hand with "Primacy" which simply means that the fact of an item having been presented earlier to the subject increases its likelihood of being remembered. This is why lawyers that shoulder the burden of proof seldom waive an opening statement since they have the opportunity of going first.