I'm collecting data on all the confirmed entries for an update to this study I did in 2016 on meme origins and I've noticed that neither In Soviet Russia nor 2013 SimCity Release Controversy have added dates where they should be (just under the title). When I check their edit histories, the green "First Created" row that's supposed to be in every entry is missing. I'm not so concerned for the integrity of my data as I can roughly place the dates at March 13, 2009 and March 8, 2013 based on their adjacent entries in the list (and I'll only be looking at years anyway), but I'm more curious why these edits were wiped from their histories and why they no longer show these dates. I assume these dates are still somehow stored as I found the entries in the list of all of them sorted by date added.
If there are more entries with this problem, I haven't seen them yet (plus I haven't looked at any submissions or deadpooled ones, but I don't recall ever seeing this on the site).