FJT - that is probably true of many members!
We have a problem with adding eBooks to the EYB Library. For some odd reason Amazon does not list the ISBN on their eBook listings and as we use Amazon for our data imports and as the ISBN is the unique edition identifier, we are unable to import data for eBooks. We don't have the resources to add all this data manually. Amazon also would not list eBook editions for other platforms they do not own such as Kobo and Nook, each of which will have a different ISBN number.
In the past we imported book data from Nielsen who did supply eBook data so that is why you will see older eBooks listed. Please do let us know if you ever come across eBooks that should be linked to an indexed print book.
It's possible in the future this may change – either because we get another source we can import data from or because we add a feature that allows members to add their own book data (this is on our development to-do list).
For now I suggest that you set up a Bookmark eBooks that you apply to all the print books you add to your Bookshelf that you actually own the eBook for. Then when searching for recipes you can filter the results to just see those you own digitally.