If you used a toolbox like OSWeb, that usually sends result data after every trial (which we think is too much and overloads the server). In that case, you would be able to see any data that were sent to the server up until the point of reload. If you programmed the task with (say) jsPsych, and submit the data only at the end of the component, then there would have been no chance for the data to get transferred before the reload.
So, essentially, JATOS will let you see any data that is in the server, but if there were no data transferred, then the data are not there to be seen.
Hope this helps