Dumb and scary mom moment

I'm going to try to keep this real brief but yesterday the hubby, LO and I went to Costco and we let LO chew on the coupon mailer that costco sends out.  Well we'd periodically check it to make sure she hadn't got any paper and she hadn't so we continued to let her chew on it.  We got home and had a very typical afternoon.  I fed LO around 5:30 and she would not eat her avocados. She loves them so we knew something was up.  I went to make her oatmeal and hubby and the next thing we knew she was choking and then threw up with streaks of blood in it.  In her vomit we find the little plastic sealer sticker that Costco puts on the mailer. The streaks of blood in the vomit freaked me out! She acted like nothing happened afterwards. She was laughing and eating and having a good time but we still took her to the ER afterwards and I'm happy to report everything was fine. I feel like the worst Mom because this could have been prevented and seeing blood in her vomit was really scary. 

 Lesson learned :DON'T LET BABY HAVE COSTCO COUPON BOOKS ANYMORE