How to recover deleted Text messages

I got my Iphone4 couple of days ago and is working fine.. Today by mistake I deleted very important messages conversation which i have saved from past 2 years on my iphone3g....

I tried to connect Iphone4 to iTunes account but its not bringing back that conversation...
Is it any possibility i can get those text messages back..

All those text messages are still on my iphone3g and i have connected that to iTunes accounts for backup but its taking forever, just hoping to get my text messages back on iPhone4 ...Any help..

I really need that conversation back at any cost.. Please help me.. I shall be very very thankful for this...