An unknown issue with Twitter is causing heavily retweeted posts to disappear from the site, including Ellen DeGeneres record-shattering tweet from the Oscars this month. The permalinked page for the tweet, which included a selfie taken by Bradley Cooper of DeGeneres, Brad Pitt, and other stars, now leads to a notice reading Sorry, that page doesnt exist! The same issue appears to be affecting The Verge and other accounts with large followings when their posts receive a significant number of retweets. …