Wrong book

I just realized the textbook I have for my online class is the wrong one.

We didn't need it for our first assignment, so I haven't pulled it out until now.

I bought it from the campus bookstore...walked in, told them the two classes I was taking and she handed me two texts. I didn't pay attention to their titles, just paid for them and left.

Now, I'm hoping they'll take it back and give me the one I really need!