I'm afraid that if the call lhistory has gone from your phone, it's gone. A lot of devices, especially ones with limited storage, manage these records on a first-in/first-out basis, though yours doesn't seem to be keeping them that long.
If this is something you might be wanting to do regularly, you could look at one of the backup apps. I used (I think) SMSBackup when I got a new phone and wanted to transfer these histories (most of the apps will do call history as well as SMS). You can store the records as a separate file, usually .txt or .xls that can be read anywhere. I used the app once and then deleted it, but there are options to take an automatic backup at regular intervals. If you do that, you'd need to make sure the file doesn't simply get over-written, of course.
