I'd classify that under coincidence. Between the test and live servers I've opened about 6,000 - 7,000 chests by now. I haven't seen anything like that. I believe it's happened to you. These things do happen in a pure random system. A managed one would be artificially kept much more innocuous-looking to avoid raising suspicion. A completely random one is free to cough up stuff that's too unbelievable for any respectable fiction. I once saw a sheet of paper slip from the top of a file cabinet, do a somersault and slot it's end perfectly between the lip of a closed drawer and the body of the cabinet. Then it just stayed there, hanging, all smug. I pulled it out and it was a tight fit. If that had been filmed, not a body would believe it wasn't CGI. It was totally unbelievable. It still happened. That's true randomness for you.