Is there any requirement for master plan for a resale flat

Hello Sir, I need some important information from you. I am going to buy a resale flat in Apartments (G+2 concept). First floor is mine. No all other flat owners in the society are staying there on the basic of allotment letter But the flat which I am going to purchase is a registry case. Owner has a registry for this. And he had mortgage his flat to HDFC bank and now it is free from there. No body in the Society has a copy of master plan. But Bank is saying that there will be no problem of new registry because this is approved property by us (Bank). and the owner has registry so it means the master plan was also approved. Now Agreement to sell has been done. Registry will be on next week. Is there any requirement of the master plan still? or will revenue inspector asked for this? Everybody including bank and other sub-registrar's are saying there is no need of it because the owner has registry with him and new registry will be done on the basis of old registry.Please resolve my issue with your perfect answers. Waiting................