Is the Stagefright virus getting smarter?

[AC Question]

After hearing about the Stagefright virus (that infects your phone by sending it an MMS message), I did what the tech websites said to do and turned off auto-retrieve for MMS messaging. Sure enough, earlier today, I received an MMS text from the phone number "1." The contents didn't download because of the precaution I had taken, but nonetheless, two videos (that I didn't download or record) appeared in my photo gallery in a new album titled "0."

After deleting the videos, I ran a scan with the standard Antivirus app that Google provides and it didn't register any problems. I wasn't convinced, so I tried to download a Stagefright detection app, but because of an "error," it didn't work. I tried downloading a different Stagefright detection app, but the same thing happened. I thought there was something wrong with Google Play on my phone, but then I downloaded another app without any problems shortly afterwards, and my subsequent attempts to get Stagefright detection apps continued to fail.

Is all of this nothing, a different virus, or an evolved version of Stagefright that can attack your device even if the infected message is not opened, downloaded, or played and then prevent you from getting detection programs? What should I do about this?

My phone is a Samsung Galaxy S3 Mini with Android version 4.4.2.