You're right, there is none; you'd either have to ask the plugin author to provide for such an option, or just pragmatically change the source code. (As there doesn't seem to be a lot if any development for FuzzyFinder, this isn't that bad an option, and you can always do the first option, too.)
I think the change has to be done in ~/.vim/autoload/l9/tempbuffer.vim
; change the second line from:
function l9#tempbuffer#openScratch(bufname, filetype, lines, topleft, vertical, height, listener)
let openCmdPrefix = (a:topleft ? 'topleft ' : '')
to:
let openCmdPrefix = (a:topleft ? 'botright ' : '')