If you can find the downloads window (Keyboard shortcut Ctlr+Shift+Y in Linux) right clicking on the file entry should give an option to open the folder it is in. If the option is greyed out it was probably only put in a temporary location and may have been deleted. You could try searching by name and date & size. You may be interested in * [[What to do if you can't download or save files]] Note you could have looked at the prefs to try to figure out the location that would have been used, but not once you have reset it. Does your distro not provide the newest releases of Firefox, you appear to be on Iceweasel 9, the standard Release of Firefox is now fx14.