Restore Removed Book - Conversion Options not restored

Calibre 8.14, Windows 10

I show a diode icon if the template function 'has_conversion_options()' is true.

I removed a book which had that icon. I then realised I hadn't taken a copy of what I had in the #notes column. So, I restored the book and noticed the diode was missing, looked in database 'conversion_options' table and there was no entry for book in question.