Fail. Minutes after I made this thread, it fixed itself.
For anyone with the same issue, just give it a little bit and the background of the icon should re-appear at some point. That's what mine did.
Sorry for the empty thread!
This is an unusual event. It might indicate you need to do a hard reset to settle things internally (press/hold power & home until white apple appears). If it continues to happen periodically, there might be an app conflict or something running in the background that is slowing the load speed. Apps that update in the background or download data (such as a news app) in the background may be the culprit.