How do I change permissions or assign User Rights in Libreoffice?

Hello. A similar question to this has been posted elsewhere but the poster didn’t respond to your request for further info, so it never got answered…

I have been writing a speech in Libreoffice text. It’s fairly lengthy and would be hard to reproduce. Yesterday when I tried to open it, I got the following messages:

Users/Mancbook/Documents/Speech Draft 1.odt does not exist , then:

Document file ‘Speech+20Draft+201.odt’ is locked for editing by:
Unknown User
Open document read-only or open a copy of the document for editing.

When I try to open the file read-only or as a copy, I get this message:

Object not accessible.
The object cannot be accessed
due to insufficient user rights

Worse still, when I go into the Documents folder where the file should be located, it is no longer there, so I cannot simply ‘right-click’ the file and change preferences/move it/‘open with’ another program. If it is locked for editing though, surely it exists somewhere doesn’t it?

Using advice from other forums on similar issues, I’ve tried going into the hidden ‘Library’ area to search for the original document and for “Speech-20Draft-201.odt” but the search function cannot locate it. Similarly I’ve tried editing/assigning different Users in the Libreoffice ‘User’ folder in the library, but I cannot see any Users in that folder to change to/from. Unfortunately I didn’t have a back-up system running (I do now!) so I cannot retrieve that way.

Any potential help is appreciated. I’m not a massive tech-head so as simple an explanation as possible would be much appreciated. Please don’t assume I know how to do anything but simple commands! I’m using a macbook pro with OSX 10.8.5 and Libreoffice 4.1.6.2

Many thanks in advance

OP: @DrAngros

I would try to reset the user profile. For information on how to do it, please refer to: https://wiki.documentfoundation.org/UserProfile

That didn’t work I’m afraid. In fact, I can no longer see the recovery file with either User now. Thanks for your response though.