The market was updated today with a new name, the Google Play Store (I know, I hate it). Along with it came a new icon, a multi-colored triangle. Chances are yours updated without you knowing it and just looks different.
And if it was on a homescreen, you will need to add the icon back to the homescreen. You should look for the "Play Store" in your application drawer, list of all apps).
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.