>"Which" is almost always used to set off a non-restrictive relative clause
This is not true. Virginia McDavid's 1977 study in "American Speech" showed that about 75% of the instances of "which" in edited prose were used to introduce restrictive clauses.
>One might be tempted to use "which" in place of "that" in a similar sentence, such as "The building which used to be on the corner has been torn down.", but it would be incorrect.
This is not helpful advice. The fact is that in standard written English, it's not "which" that marks a nonrestrictive clause, it's the comma. If there is no comma, the clause is restrictive whether it is headed by "which" or "that". Here are just a few examples of good writers using restrictive "which".
It was a concern which brought just employment enough. (Jane Austen, Emma, chapter 2)
However, she soon made out that she was in the pool of tears which she had wept when she was nine feet high. (Lewis Carroll, Alice's Adventures in Wonderland, chapter 2)
He lived in chambers which had once belonged to his deceased partner. (Charles Dickens, A Christmas Carol, Stave 1)
Buda-Pesth seems a wonderful place, from the glimpse which I got of it from the train and the little I could walk through the streets. (Bram Stoker, Dracula, chapter 1)
I think I can see a little into the springs and motives which being cunningly presented to me under various disguises (Herman Melville, Moby Dick, chapter 1)
and Mrs. Heathcliff leaning over the fire, diverting herself with burning a bundle of matches which had fallen from the chimney-piece as she restored the tea-canister to its place (Emily Bronte, Wuthering Heights, chapter 2)