I appreciate everybody's help on this. I am almost sure that one does not need the 797 notice once they have their visa stamped. This is the whole purpose of 797, is to obtain the visa. Once you have obtained the visa it is only for your records and POE should not ask for it. I have few friends who travel internationally on constant basis, I contacted them regarding the same issue and they said that they never showed their 797 at POE at re-entry.
I have not read anywhere anything about it and I sure would not like anybnody to take any step based on my personel observation/experience. People at POE might ask for it. They have a right to ask you regarding your immigration status and all the other documents related with it. So I would suggest that one should carry their 797 approval notice with them.
My problem has been solved. I found my approval notice. I misplaced it during my move-in.
Thanks for all the help.