I remember a similar stuff like that and i was kind of looking for means to lock my phone with a secrete code because of security reasons. One day, i really don't know what really happened that i was unable to unlock it any more. Spend the whole day without chatting with my friends and business partners can you imagine. since then, i vowed never to lock my phone.
Every phone have it's unlock code, I will recommend you to get that code for your mobile first and after that you will able to unlock your phone easily. You will be able to get this from your near by store or from internet.
By the internet you can easily find out batter suggestion to unlock your mobile. Each mobile company made his own website and it's provide a batter solution to any phone query. You are also visited your nearest store to unlock your mobiles.