It was actually through the app that I discovered Fluther years ago.
However, it almost caused me to give up on Fluther altogether because its functioning was so crippled that you could not use it to post questions, only to read them.
After having several answers vanish into the. ether I was ready to quit Fluther altogether. Fortunately I figured out that i could also access the site on iPhone via the browser and that worked (even tho the mobile browser version of the site from iPhone still has limited functionality in other regards)
So, even if you could find a copy of the old app, I doubt you would find it satisfactory.