Did you change anything else in your cart?

If it had to do specifically with the Google Analytics module, I would think it would appear on ANY page the analytics is on.

Did you alter the code on the checkout success page at all?

One area you may want to check is to make sure you have the "on_load" event in the proper directory on the server for Google Analytics.

It should have come with a javascript file that gets uploaded to the /includes/modules/pages/checkout_success directory.

Did you upload that file as well?