If I modify the source code so user_admin (or whatever it's called) always equals 1 (so the calendar icon appears), or even just type history:###### manually into the search box, it shows me the history for any simulation, even if it's not my own. Since the server obviously doesn't only allow admins to do this, I think the program should be modified to always display the calendar button. It would just make it more user-friendly, so you don't have to click "Open in browser" and copy the save ID.
History hits the server with a lot of load, the history button is hidden because it would otherwise be used a lot more, also most people aren't looking for previous versions of saves.