You can just copy one from another section of your site which should work fine, although it really depends on what was in the .htaccess file and wether or not it was actually important. You will probably have to make a new one (copying it from another place will work), and change it so that the settings are the same as the were before.
To answer you question quickly, as far as I know there is no way of actually getting it back, if it is a major issue then post in the support forum and get an admin to put a new one there.