From Frequently Asked Questions
http://www.vinagames.com/?F=faq#account9
How long I could leave my account unused? Why was my account reset? Why did the server remove my account?
All unused accounts are removed. If you don't play any game for 4 months, the account is reset to its initial new account state. If you do not login for 6 months, the account is completely remove from the system, and anyone could register again for that nick.