Spun off from bug 1533574, in which I landed a workaround that doesn't really fix the bug. jdescottes pointed out the real issue on review:
I think the issue is that since I landed the original fix we now change the runtime name displayed after connection / disconnection.
So the removeUSB helper should check both that runtime.name and runtime.shortname are not found in the sidebar. Feel free to land this but we should file a follow up to implement the correct fix