Google Sheets: Why are there missing submissions?

Ok, I found the submissions in searching for them but they did not make it
into our Google sheet. That is where we were expecting to see them and they
are not there. Should we not rely on Google sheets but use the downloadable
Excel file? ​
...

Apologies for the inconveniences this may have caused to you. 

I already sent the missing submissions to the integrated spreadsheet with your form "72446491586164". Please note that this may have happened due to a temporary issue with the current integration, if the issue persists you may need to re-integrate your form. 

I hope this helps.