What the heck happened to my WoW.exe file?

I was playing on Lordaeron last night, no problems of any kind. I turn on my PC this morning, open my folder to play some WoW, and WoW.exe is no longer there. I searched up and down every folder in my Warmane 3.3.5a directory and every other file is accounted for, but WoW.exe is gone as if it just fell out of my PC or something.

What in the hell happened? I certainly didn't delete it...

It's likely that your antivirus moved it to quarantine. Make an exception for it. Also can you tell me which antivirus you're using? Seen this issue recently a few times so one of them had to have an update that changed the way it behaves towards pirated software.