Current day's SAP transactions are missing from the SQL Database

HI Experts,

SAP version : 8.81 PL07

SQL Server  : 2008 R2

on 22nd Feb 2013(Yesterday) our SAP user are busy entering Transactions in SAP. By 2 PM we expanded our Vmware based Server Hard disk and restarted our server and login to SAP server. We Found the current day's (22nd feb 2013) transaction is missing.

I realised as roll back scenario .   i am clue less.

can you experts, say what could be reason in my scenario and also what are all will be the reason to sudden missing of data of particular day's ?

Note: For the information, we have not take the previous day back up and restored .

thanks in advance,

Regards,

Dwarak