Getting Timesheet with TimeEntries

I've been tasked with creating partial timesheets for users with data from a third party system. In order to do this I need to search for existing time sheets for a particular user to see if they already exist and then see if I can add time to the timesheet.

I have managed a simple search which has returned my previously created timesheet but it has not brought with it the existing TimeEntry records. The timeGridList field is null.

     public void GetTimesheet() {          // find me        var usr = GetEmployee(122);        var usrId = usr.internalId;          RecordRef usrRef = new RecordRef() {          internalId = usrId,          type = RecordType.employee,          typeSpecified = true        };          // look for timesheets        TimeSheetSearchBasic tssb = new TimeSheetSearchBasic() {          employee = new SearchMultiSelectField() {