Forgetful parents are one thing, but when they fail to tell you they're going on vacation, that's a whole other can of worms. I remember my parents once forgot to tell me that they were visiting my state. When I found out (via pictures on Facebook, mind you) I was absolutely livid. I could have taken time off to spend with them but instead, I was stuck on a big project and couldn't drop everything at the last second. Plus, I didn't even really want to see them at that point. How could they forg…