Letter Openers

A few weeks ago, I mailed essays from my ENG 291 class to students who had turned them in the last day of class. One, an essay condemning the Patriot Act, somehow opened at the Post Office and was taped shut. The paper itself was lost in the mail (only the envelope arrived).

Since then I've noticed some of my mail has been opened and taped shut. This could all be chance (letter writers forgetting to include something, opening the letter, then sending it again) but it's getting disturbing. I doubt if I'd have noticed it if my student hadn't contacted me about her paper.

Has anyone else had this happen?