When you are rendering to disk you get a message in the bottom left hand corner saying "Rendering to disk: 2% - Time left: 0h25' - Press Escape to stop rendering". You don't get a progress bar. The render size that you have chosen is very high. I just did one about that size and it took 258 hours to render, so your render would probably have a long way to go. You shouldn't be able to click on any menus or anything, so sounds like it may have been failing or have already failed. There is a bug in Vue Pro that will give a quick render of that size (in about 2 seconds) and will indicate a complete render but won't actually render anything. Once all this has happened you will find that Vue will continue to run at 100% until you kill it. Sounds like your scene is saved, so that is the important thing.