Did you know that there are free services that archive the web constantly, and allow you to go back and look at URL's through time? One example I use a lot is Internet Archive WayBack Machine. If this happens to you - the first thing to do is DON'T PANIC (yes, intentional reference to Hitchhiker's Guide).
Second, hit your browser's Back button (or go back to the page that has the link you want). Right-click, and depending on your browser pick Copy Link (or Copy Link Location).
Next, open a new tab and enter "archive.org/web". Finally, paste the URL that is gone into their search bar, and you will see a calendar graph of updates to that URL throughout time.
The black bars show when the site changed, and you can click the month, and the date in the calendar below to see the page at that date.
That's all there is to it! Hopefully this saves your hair from being pulled out. Poor hair!