Hi 
It 'should' be really easy to "de-minimise". Writer 'should' have a small tab-type thing in your taskbar/launcher/panel/whatever to show that it's still open and clicking on that 'should' bring the document back.
If it's "just kinda disappearing" then maybe it's weirdly gone to a different workspace without taking you there at the same time. Try
Ctrl Alt and the keyboard arrow keys
Most distros give you 4 in whichever DE you happen to have chosen. SliTaz and some others might give just 2 so i press the Ctrl Alt left arrow about 4 times to see what is open on other workspaces.
There is probably some fancy work-space switcher and if you just click and hold down on that it might show you all 4 workspaces at the same time.
However, it just sounds like LO is just misbehaving, perhaps needs a dependency fixed or updated or perhaps a weird tweak or something or maybe an Extension misbehaving. On my version of LO on this machine it is behaving as you would expect so yours is not behaving normally.
Regards from
Tom 