Unusual message at startup and home page cleared of apps.

[Aelvir]

My phone is a Virgin Mobile Alcatel-onetouch.
So, I finished charging my phone while it was off, and turned it on, and When it turned on swiped left for it to go to the camera because I needed to take a picture of something then it paused for a moment then showed Virgin mobile logo (the same that shows up when the phone starts turning on), then I'm at the home menu of my phone and a message reads "Congratulations! The Setup Wizard is complete!" And all my apps are no longer on my home page! The only ones on the home page (except for the Phone, Camera, Messaging, and Chrome ones at the bottom) were:
Left page: Calculator, File Manager, Notes, Sound Recorder. Center page: My Account, Google, Play Store, Voicemail. Right page: -blank-
So, I pressed the button between Messaging and Camera and it opened my Application list. All my apps are still there,they just were removed from the home page for some reason. And I double-checked and everything else seems fine. All it seemed to be was an inconvenience but, I want to know why this happened and what may have caused it.