Well, truly, you got exactly what you asked for, even if that isn't what you wanted.
At this point, just throw away the pre-render and replace that section of the timeline with the original composition. Or pre-render again, with different settings. The original composition is still there.
However, there's a fundamental problem with your action of pre-rendering: when you pre-render a composition, you must do it using the same final output settings as your entire video. "Pre-render" means exactly that: you are rendering the same way you will render your final video, but you're doing it in advance to save render time while you're editing other stuff. Take a bit of time out and read the entire precomposing, nesting and pre-rendering page in the After Effects online help.