When R1 disapprear, R2 does not need to "re-associate" to the ZC, so it will never appear in ZC association table. If R2 is within radio range of ZC, it will appear in neighbor table.
Why are you even looking at these tables anyway? Association, neighbors, routing, etc. are all problems that have been solved for you by the Z-Stack which implements the correct ZigBee specifiied behavior.
What exactly and specifically is the problem that you are trying to solve with ZigBee which you cannot solve, or are having a problem solving with the Z-Stack.