Yeah, they're super-strict about these sorts of things. If you touch a book or your cell phone, it's against testing regulations, and your test will be canceled.
When the mistake is an innocent one, it's not the end of the world. You'll be able to take the exam again in the future, and unless you actually cheated, it won't do anything to affect your odds of b-school admission. It's just a stressful irritation that postpones your exam. It's not fun, but think of it as an extra 30 days to hang out with us here at GMAT Club and study for the exam.
Here's a much better thread on what NOT to do at the testing center, for anybody who isn't sure what the rules are:
https://gmatclub.com/forum/10-things-no ... 20625.html