I have been using gimp for probably 10 years and to this day I still don't know what happens to my tool options window. I'll be working and suddenly the tool options will be gone and I've spent a lot of frustrating hours trying to find it and figure out why suddenly takes a dump. Every so often the gimp interface gets impossible to figure out and resurrect so I have come to the place where I just have to uninstall gimp and reinstall the next time i need to use it. Don't think there is a clear reason or solution-I'm just complaining because it is annoying-but it;s free.