It just happened to my wife this weekend: she'd written a review of her trainer that showed up at the time, but at some point in the last few months it disappeared from the trainer's page, even though it still appears within her profile. She updated the review and it then appeared to her when viewing her trainer's profile, but it didn't show up if she logged out or when logged in from my account.
Simply deciding not to show reviews you've written and/or randomly taking them down after they've been up? Sketchy. Showing those reviews to you so you think they're there even though no one else can see them? Ultra-sketchy.