There's a little button that allows you to collapse the toolstrip, if you click on one of the tabs (HOME | PLOTS | ...) the toolstrip will show again temporarily, if you double-click (or click the little pushpin on the right after clicking once) it will show up again.
Once you've got the toolstrip showing, I'd suggest going to HOME -> Layout -> Default, which will restore the default layout.
The circled button at the bottom right collapses the toolstrip, click one of the tabs to show it:
Either double-click a tab, or click the circled button at the right to keep the toolstrip pinned:
Once you can see the HOME tab, choose Layout/Default to restore the default layout: