That's very much a possibility. The twitch launcher isn't available on Linux so I can't test it. I'm using MultiMC which moves the .minecraft folder to a different location (so you can have multiple instances) and the twitch launcher might do the same thing.
Try clicking the "Open Replay Folder.." button in the Replay Viewer GUI screen, it should take you to a folder inside the correct .minecraft folder.
Could you also post the contents of the fml-client-latest.log file inside the log folder inside your .minecraft folder (wherever it might be) to some pastebin site and link to the post here.