Default Decryption Password


I own a mobile phone shop and today there was a guy who trade in a Moto G for a brand new Note 3. Everything was fine when I tested the phone. However, just minutes ago, the phone started to ask decryption password. Is there any way for me to get this phone back to its original state?
LG Optimus 2x
PA 2.6 v13 KK 125