Yes, but that dynamic creation has nothing to do with what IP you came from or are using, otherwise I wouldn't have got it for a second time, based on your assumption you only get served up to you once.
Pages that are created dynamically are normally because the page content changes and requires something like PHP which this site uses, is vulnerable to being hacked if is using an old version. The actual templates can be infected, but it would have to have some additional processing in that PHP to check the referrer or user IP to serve up a different template with the inserted code.
I don't believe it is a caching thing on my system, as I refreshed the Page (shift + refresh or shift + F5).
However now the index.php isn't bringing up this inserted script after the closing HTML tag (as I said a standards no, no and highly suspect) and no reference to 7879 in any of the page source code; so we will have to see if it has been cleaned.