You don't see it in the plug-in chooser? It's possible to remove any of the track level effects so that they don't show up anymore. It's also very easy to add them back in any combination you choose. Open up the Track Effects window and then click on the little green icon in the upper right corner that looks like a rectangle with ears. This opens up the plug-in chooser and gives you a list of effects you can add. The similar icon with a red X on it removes plugins from the chain, which is probably what happened in your case.
However, a much simpler solution may be to "reset" Vegas back to it's original installation state. Quit Vegas, then hold down Ctrl-Shift while you start it again. This restores all functions, options, parameters, settings, and layouts back to the factory defaults. It's a heck of a lot faster than reinstalling. However, i suspect that my first paragraph is an even better step.
For future reference there's a method that's much much faster and easier than a reinstall. Hold down the Ctrl & Shift keys while starting Vegas. This sets all options, preferences, templates, and layouts back to the original installation state.