Looking at the comments something that caught me out when working with indexedDB from the service worker is that it the extension has it's own area for the db.

When saving from a content script it saves to your browsers indexedDB

When saving from the service-worker it saves to the extension indexedDB, the easiest way to open this inspecting your popup then going to the application > Indexed DB

This might be why you couldn't find the object store from options_page. You might have to do some syncing up to make sure you are saving to just one location.