What led to this:
I went into design-> widgets to change the WP-Polls mode from "Display Random Poll" to "Do NOT Display Poll." This was all it took to make the entire sidebar disappear from the index page. I also changed the positions of the widgets by dragging "Meta" up a few notches.
Ever since, no matter what, the sidebar simply does not show on this page. However this is the only area where this problem occurs. This does NOT happen when viewing single posts and other pages.
What doesn't work:
Deactivating WP-Polls plugins.
Removing all widgets nor adding them back in.
Resetting Polls to show as before.
Changing the positions of widgets in their original order.