Changes in shared document magically disappear, despite not showing problems with syncing.

I tried to be as descripitive as possible in the title, but essentially what happened was this: 

I have a shared cloud document with a coworker. The document has been open on both our computers without closing for a couple of days. I have been doing design changes in the document, and it has shown no signs of sync issues or otherwise. When I came back to work the next day I saw that some of the latest changes I did the day before was no longer there. Keep in mind, I had not closed the document. Just left my desk in the afternoon and opened my computer the day after. I thought this was a bit weird and checked document version history, but none of the synced versions had the latest changes in it. But I kept on working in the same document for a couple of hours before I had a meeting. Again, XD did not provide any signs of issues with syncing whatsoever. The document remained open in XD until I finished the meeting and started working in the document again. This time too, all of the changes I had done since I started working that morning, was lost. There were no versions in document history from around the time i stopped working to go into a meeting. Latest version was from that morning. I asked my coworker whom the document is shared with, and he too had had the document open but without making any changes to it, and was unable to see any other versions that had these changes saved. 

So it seems that at least half a day of working is lost and aparently not possible to retrieve through version history. In fact, it seems that the document has not synced properly, even though there has been no signs of sync issues. 

Is this an issue with shared documents? Is there a way to retrieve lost changes?