It was just another irregularity encountered by my iPhone and such had caused me another count of paranoia.
Just the other night, I let my cousin used my phone to communicate with our common friend. After a while, he returned it saying that our friend has responded but he cannot open the message. I've noticed that something showing "download pro" and a dialogue box for new message appearing on the screen. I tried to touch on "view" but nothing came out. I slid my finger on the cancel button but it didn't work. I hold on the power button till the slide to turn it off emerged. However, sliding the same thing has brought me into nothing. I assumed its system hung already. I asked my friend to call me. She can reach my iPhone, it was ringing but still I cannot slide the screen to answer the call. So I just let the night passed without any plans of taking it to the service center.
Right upon waking up, I immediately put on my desktop with the intention of searching through Google on the possible resolution to my problem. With enough of patience, I browsed every link which has something in relation to my iPhone's problem. The first two links I've visited didn't give me the right answer tnd so my third time was the very fortunate try I've done.
I just followed the first instruction which says "hold (long press) the home button and the power button at the same time till it takes your iPhone to restart". For about 5secs I hold on the buttons then my iPhone restarted. After another 3secs or so it asked for my PIN and that resolved the issue. My iPhone's working again.
Thanks to Google.