New phone has missing iBooks audiobooks

Audiobooks (and tones) are a one-time only download from the store, an iCloud restore will not redownload them. If you had them on your old phone then did you copy them from it to your computer's iTunes library via File > Devices > Transfer Purchases (they should have gone into the Books/Audiobooks section of the library) ? If you did then you can sync them to your new phone

It's not documented anywhere, but (to many people's surprise) iCloud backups don't seem to include audiobooks.

See: Does iCloud backup include audiobooks bought through iTunes.app?