Answer
This points to the customization having been made as a direct, ad-hoc edit rather than through the proper supported landing-page customization mechanism — a landing page customization built following IFS's documented Landing Page Development process (as a real Developer Studio customization/component, deployed properly) survives deployments and reconfigurations the way any other customization does; a direct edit made outside that mechanism doesn't, and gets overwritten every time. Rebuilding the customization following the documented Landing Page Development steps, rather than editing the landing page directly, is what prevents it from being rolled back on the next deployment.