My screen was never loose on the edges but only in the centre of the screen, so you couldn't actually see a physical defect on the phone.
So the Apple Genius guy wanted me to replicate the problem. But I couldn't, this was probably because I drained my battery and charged it up to 100% in one go 5 hours before I went to the genius bar. When I was charging the phone it got a bit warm, so I think the adhesive was warm enough to stick itself back together again? The popping sound was very faint after charging my phone, and I pressed my screen pretty hard as well. So I might have stuck the parts back together. lol.
Anyway the guy said he'd take a look at the screen at the back of the store (10 min wait) and when he came out with my phone he said he found nothing wrong with it, so he couldn't call in a repair service or exchange it.
To him the phone was rock solid and there was no popping sound - the edges of the screen were locked in place. He said if there was any problem with the phone again just book another appointment with the genius bar and someone will check it out.
Now I'm back home and the popping sound is gone - the phone is rock solid again. For all I know, the sounds might come back again in the next few days...we'll see
P.S Besides we still have a year's worth of AppleCare to go through, and that thing covers repairs as well.