You can get the file back by right clicking on 7dtd in steam and selecting Properties, Local Files and click on Verify integrity of game files.
My virus scanner detected and deleted my launcher as well, this has happened with an earlier version of the game A15 I think as well till they fixed it.
Replacing the file will probably only get deleted again by the virus program. You can however start the game using 1 of 2 exe's in the game directory without the launcher.
You will find it here on your hard drive it is installed on \Program Files (x86)\Steam\steamapps\common\7 Days To Die
the exe's are 7DaysToDie and 7DaysToDie_EAC.
Hope this helps.