Does my phone have a virus?

I have a smart phone and I was searching for some things on google until I saw at the notifications bar that something was being downloaded. I looked at what it was and it was some program with weird letters and I was sure that it was not an update, and I knew it was a drive by download. I have none of my apps update by themselves. So I went to the notification bar then a message said, download was unsecessfull. Then it stopped and I went to download history and deleted everything there. I turned off my phone that turned it back on then ran some scans using lookout. It said everything is ok. I am still worried. Does my phone have a virus because I don't even know what any of those things mean.