The F80EXR has a few issues with auto focus. One of them is an issue it shares with the F70EXR and indeed, I’d bet with most Fuji cams. This is the tendency of Quick AF mode to overlook the most contrasty object in the scene.
This is an understandable failure, but you must be aware of it when working with this camera, or you will be in for a lot of confusion.
I first noticed the issue when testing the camera in Quick AF mode, thinking that this would be a nice way of working. But right away I found that there were scenes it could not focus on. Through a window, specifically.
It turns out that the EXR cams (and perhaps most Fujis) drastically shorten their focus range when in Quick AF mode. Here is a classic scene showing the issue.
Now, I’m not trying to say that this is somehow an error on Fuji’s part. I’m quite sure that this is the appropriate behavior for anyone who uses this mode. But it will catch you when you don’t expect it, so I would suggest that you only use quick AF when you are shooting fast moving objects with nothing confusing in the foreground. The cam gets easily confused.