There are no web statistics logs on server for a particular date or before that.
Are the log files of the other dates renamed and statistics calculated?
The log files are removed due to log rotation settings for the domain: by log file size or by time. Old files that are out of rotation condition, were removed. The statistics are calculated for the dates for which the logs were not removed.
The settings can be modified at Domains > example.com > Logs > Manage log files > Log Rotation: