Q: has anybody had to recover ITunes content from an Ipod nano to a windows PC

This article from turingtest2 may help:

Recover your iTunes library from your iPod or iOS device

and this one from Apple directly answers your question:

Redownload or transfer your iTunes Store purchases from an iPhone, iPad, or iPod to a computer - Apple Support

Your i-device was not designed for unique storage of your media. It is not a backup device and media transfer was planned with you maintaining a master copy of your media on a computer which is itself independently backed up against loss.  To use a device with a different setup you transfer the old library from a computer or a backup directly to the new setup, not the device to the library. Media syncing is one way, computer to device, updating the device content to the content on the computer, not updating or restoring content on a computer from a device. The exception is iTunes Store media purchases which can be transferred to a computer.

Re-download or transfer your iTunes Store purchases from an iPhone, iPad or iPod to a computer - https://support.apple.com/HT201267 - "This feature works only for content bought from the iTunes Store." As of iOS9 it no longer does apps which now must be re-downloaded directly from the Store.

For transferring other items from an i-device to a computer you will have to use third party commercial software.  See this document by turingtest2: Recovering your iTunes library from your iPod or iOS device - https://discussions.apple.com/docs/DOC-3991  Even this method may not fully recover what you had in the library originally. For example if in order to save space when syncing you had converted music files to a lower bitrate, or photos to a lower resolution, it is those lower quality files you will recover.

If you subscribe to Apple Music, tracks which are not part of content you have purchased or uploaded cannot be transferred and have to be downloaded directly from iCloud.

For other items see:  Import photos and videos from your iPhone, iPad, or iPod touch - https://support.apple.com/HT201302 - these are ones you have taken yourself.

See also Recover media from an iPod. Recovery using just Windows Explorer or Finder for non-iOS devices.

tt2