The article about Mabel that Wally reads to Joe is different from the article visible when they show it to Mabel.
Ruber's vision/hallucination shows a LIFE Magazine lying open on a table in the Room, presumably at the moment of or immediately preceding the unknown Event of 4 May 1961. Later, when the Sood is searching for information relating to the Occupant, we see a brief glimpse of the cover of the same issue of the magazine in his computer's "Object Catalog Scan." But the date of that issue - which features Eisenhower on the cover - is from 7 July 1961, so it can't possibly have been there before or at the time of the Event because it literally didn't yet exist.
Kreutzfeld tears a page from One Flew Over the Cuckoo's Nest to verify it is not an object. However, all the objects were created in 1961, while the Kesay novel wasn't published until 1962, so the test was unnecessary.