Perhaps you have been making some updates on this as I do not get the 404 error message page, instead I get to the details page with a message saying that there are no results for search.
When I look at the link for your learn more button I can see that there is no URL parameter present for the id. Rite now the link to the wolf art when clicking on the learn more button looks like this:
like you noted the URL should look like this:
Based on the code that you have for the learn more link it seems that this id should be present. If you can please post back with a copy of your index page and I will take a look to see if I can spot the problem.