You should start with making a backup of this file together with the file with the same db name with extension .journal.
The normal database process (approximately) is that any changes you make while the db is open are marked in the database and are written in the journal. Once you close Cross (or change collection) the journal is applied to the database file, making all changes permanent.
Your battery like died at a moment or the shut downproces caused the files to become out of sync.
WHile you have your backup safe you can try the following:
1. verify the file attributes to make sure there isn't a simple 'in use' state of the files.
If so, change and start Cross to see if this was it.
Else
2. copy the files to a new name (just to avoid using the backup file)
delete the original .journal
start Cross
If this works you'll see you have the database back to the state before the start of your error session.
If this doesn't work, send your backup (2 files) to
support@mixvibes.com and maybe they can fix it for you.
Important lesson: don't forget to occassionaly backup you collection, so you max loose a limited period of effort...
by chance have you created other collections ,, ie from earlier versions ,, there is a tab for loading collections ,if there was more than one then this is where it will be ,, 
