Um, Hello. The Ark was not necessary to demonstate Indy was in the same warehouse. It was apparent from the first shot inside the building, and everyone recognized it with a happy gasp at every screening I saw.
Referencing the Ark is a new rule for each Indy film after
Temple of Doom (there was an Ark reference in
Last Crusade as well), to point out how infererior all the sequels are to
Raiders of the Lost Ark.
It's the truth.
