OK so I took some time today to try and recreate the missing toolbar issue and if I could achieve losing it what did I have to do to bring it back.
So I managed to create a missing toolbar by doing the following. I have a 3 Screen setup - a laptop screen plus 2 high res monitors left and right of my Laptop. I created some Floating Toolbars and had them on my Laptop Screen along with TBC. I then saved the Menu Configuration using Support - Customize Menus - Export to save a file - with the Toolbars on my main monitor. This acts like a restore point. If all else fails I can get back to this point easily using the same command and Import the menus.
The Exported Menu Configuration comprises four parts - The Menu Ribbons and those which are turned on and off, the Custom Toolbars, the Quick Access Toolbar and the Customized Keyboard Shortcuts / command aliases that you have created. When you import a Menu Configuration, it will reset all of those to whatever your saved configuration looked like at the time of saving. This includes the last location of the Toolbars - where they were docked or floating on the screens at the resolutions you were running at (be aware of the resolutions thing, if you change resolution and windows will do that to you if you are working in a field mode and office mode with multi screens and different resolutions in the office and just a laptop while mobile) because that alone can make a toolbar disappear (it was located in a high res space and now you are at a lower res and the toolbar is in vapor space off screen somewhere and you cannot see it or control its movement until you can see it.
I moved my floating toolbar onto an external monitor and then disconnected that monitors from my docking station - the toolbar still thinks that is where it is and will not show up on the residual screen real estate. I did not try rebooting to see what happens when I restart with a different configuration. Anyhow, I then reconnected the monitor, and the toolbar that was on it before did not reappear. When I ran the Customize Tools command however when that command dialog was open I could see the toolbar that went AWOL on me and I could move it onto my main monitor, and after that I could close the command and it would remain where I left it. While the command was open, you could switch the toolbar On and Off using the options in the first tab of the Customize Toolbar command to get it to show up, but it would disappear again while it was on the second screen when I closed the dialog unless I moved it back to my main screen.
I found that if I used the Customize Menus command and imported my restore point configuration, in all situations it brought back the toolbars to the place where I had saved them in that configuration.
Moral of the tale here - if you want to Float Toolbars - make a restore point Menu config file with them on your Laptop Screen so you can get them back if you lose them. Be wary of floating them off your main screen if you disconnect and reconnect monitors or change screen resolutions deliberately or accidentally or courtesy of Microsoft or if you plug in and out of a docking station regularly during a days work.
I hope that this helps and shines a light on the issue and how you can solve it. Let me know if it does / doesn't assist and if it doesn't can you tell me what you think you did to lose the Toolbars in the first place.
Alan