Comment by Kon-Peki

Well, your cipher text could decrypt to a non-published URL that has some cipher text which decrypts to another non-published URL (as many layers of indirection that you need), with the final non-published URL containing the actual cipher text you wanted to decrypt.

You can check server logs to see if those URLs are ever hit.

And if you ever need to, you can abandon the original link after changing what those non-published URLs point to (something "fun", like a rickroll perhaps).

In fact, how about using the Wayback Machine to store a bunch of versions of the static page, each containing different versions of the cipher text. Only you know which date range contains the proper cipher text!