Since I had a similar question I'll add some words here.
I had no padlock icon and there are no toolbars at all when I open a locked dockument. If I close the document I can make toolbars visible in the View menu (View / Toolbars / Quick Access Bar). This will remain open when I again open the document.
The help file says:
View Only 12.0
Produces a book or document that you can open but cannot edit. If you accidentally save a file in View Only format, you can make it editable by pressing Esc Shift+F l (lowercase L) k. Then you can save the document or book in Document or Book format.
This works, but be sure to do it exactly as it says. In other words:
Press the Esc key (release the Esc key)
Press the F key (UPPERCASE F, and release it)
Press the l key (that is a lower case L. Release the l key.)
Press the k key (release the k key)
Also, make sure to click in the document before unlocking. It seems unlock has no effect when the wrong parts of FrameMaker has focus.
Now the menus are "full", and the document can be edited.