What version of windows? If its Vista+ then getting it back is easy peasy.... enter VSS ( a godsend for situations like this)
Right click on the folder where wallet.dat should be, select 'restore previous versions' ... if VSS is set up properly on ur system you will see several folders listed w/ date stamps .. if so, just open a folder that has a timestamp before your wallet.dat went missing, and copy wallet.dat out of it and into the spot where its missing.
Problem solved.
WIN 7