Where exactly is the ESN built on the IPhone 4 Verizon Version ?

I had a verizon iphone 4 16gb with a bad ESN, I was just using it for my music and videos and wifi, however since the power button stopped working out of nowhere I took it to the apple store. I never told the Apple Genius that the phone had a bad ESN, so he said the phone needed to be replaced because of the power button. So he gave me a new verizon phone. Do you think that now since he exchanged it the ESN will be clean on this one ? He asked me if I want to activate the phone but I chose not, I told him I will do it at home because I don't have the information. Please let me know if you think the ESN with this new verizon iphone 4 should be clean now ? Thank You. !!