Running into this extremely annoying issue. I start a file transfer, and continue doing something else. When I go to check on it, the file copy dialog is no longer open. I can't alt-tab to it, and it doesn't show up in the start+W window overview. The file transfer is still going, because the Files icon still has a progress bar on it. Right-clicking on the icon and clicking "Show copy dialog" does not bring it back, but clicking "Cancel all in-progress actions" does seem to cancel the file transfer.

How do I fix this? Is it fixed in 15.10? This issue is intermittent, so my quick test from the 15.10 live ISO didn't yield any conclusive results. It worked fine there, but it works fine most of the time in 14.04 as well.