how do you say "oops" in Spanish?

I start my Spanish class this evening, and am very excited about this. (Cue sniffing new spiral notebook...ahhh).

However, I forgot about one thing. Textbook. Now, when I received my registration confirmation/payment receipt in the mail, at the bottom was a note reading "Textbooks not included." I read it and thought nothing more of it.
This was...a month or two ago.

Fast forward to today when I looked up the address for the class meeting online. There was a new link under course description for "textbooks". I click it and - lo and behold - there is a text and a workbook listed there. But, there's also a note reading "textbook optional," but only under one of them. So . . . ? Not sure. I click the link and it takes me to an online store to purchase the texts, where - in big, red, bold letters - it reads "REQUIRED." But the course descprition said optional. Hmmm.

I'll just be "that guy girl" who shows up on the first day of class without a textbook. I hate that. (The perfectionist student part of me is alive and well, so it seems...) Luckily, my adult brain chimes in with a "well, it's not like your permanent record matters or anything - you'll be okay".