Hi @emily,
just building on @Chris_Hofer 's reply, the link goes to the Canvas 'Free for Teachers' site, which suggests that the resource was created privately outside of Instructure and (if you had sight of it) was initially public.
The 'access denied' message suggests that the resource has been changed from an open resource to an enrolment based resource - to get access you would need to be able to track down the owner and be added as a user. I don't think that is going to be possible unless someone in Canvas admin at Instructure is prepared to 'sneak a peek'.
I don't think that it has been deleted, as I would expect to see a 'Page not found' message.