Previous experience tells that your file will be utterly corrupt. Try the methods in this post, as soon as possible, in the hope of recovering part or all of it.
The damage is possibly due to over-hasty power-off of computer or closure of laptop lid, before the file housekeeping has been written to disk.
As soon as possible try the methods in this tutorial
See
[Tutorial] How to find and un-delete AOO temporary files for detailed instructions on how to
a) use
Previous Versions (W7 and later) to recover previous versions of the file (is there something similar on MacOS and Linux?);
b) recover your file as it was when you last opened or saved it, or as it was when it was last saved with AutoRecovery;
c) find previous versions of the file in the folder it is located in, but which have since been deleted;
d) un-delete the temporary files AOO wrote while you were editing the file, and then deleted. This will recover your file as it was when you last opened or you last saved it.
There will be nothing usable in your damaged file - waste no time with it. Try the recovery methods above.
| Edit: For a Mac many of the procedures outlined in the tutorial may be irrelevant. Try downloading PhotoRec and letting it recover temporary files. |
| Edit: If the error was in Saving the file, have you sufficient space on the target hard disk; have you also rights to the folder in which you tried to Save it? |