French Pronunciation and conversation question

In lesson 9.0 Your Weekend, question 4, why is the correct answer "Qu'est-ce que vous avez pris hier soir?" and not "Qu'est-ce que vous avez pris le dernier soir?" Le dernier soir is last evening whereas hier soir is yesterday evening. It literally means the same thing, but I feel that le dernier soir was the more appropriate translation for the question last night/evening. In 9.1 at the Concert, why is the "t" pronounced in fait.

I think that "dernier" would be used more to indicate the "final" in a series. Use "Linguee" to see usages, as I did, and there were none immediately visible for the sense you wanted.