The timestamps get relativized by HN's re-upping system, described at https://news.ycombinator.com/item?id=26998308 and links back from there. About the timestamps, there are past explanations here: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que.... Sorry for the confusion—I know it's weird but the alternative turns out to be even more confusing and we've never figured out how to square that circle.
You can always see the original timestamps by looking at any page other than /news or /item. For example, here: https://news.ycombinator.com/from?site=krebsonsecurity.com.
Not finding the post on search is a separate issue - that's because the threads had been flagkilled, and killed posts (anything marked [dead]) doesn't show up on HN Search.