There’s a one-panel mention of the Riverdale High library in “Obedience Training,” which is reprinted in World of Archie (Comics) Double Digest 72 (November 2017). Dilton says he had to go there, but we don’t see him in it.
This is a funny story with a great final panel. Mr. Weatherbee asks Archie to tell something to Mr. Flutesnoot, but Archie asked Betty to tell him, and Betty asked Jughead to tell him, and Jughead asked Dilton to tell him, and Dilton had “business in the library” so he asked Moose, who of course forgot.
Later Mr. Weatherbee needs to pass a message to Mr. Burnside (not a regular character), and angrily tells Archie he has to do it himself, personally. The final panel is Archie sitting in a howdah on an elephant, snow-capped mountains in the distance, typing a letter: “… and the guide assures me, Mr. Weatherbee, that we should overtake Mr. Burnside’s safari before the week is over! I sure hope he brought his attendance figures with him on vacation.”