Ok guys, I got back my funjet from Andrew last night and did some analysis on why it lost power completely during flight.
First up : What is still working? Well, amazingly, the servos, receiver, and even the ESC were still working. The battery was definitely a gone case. It had bloated to about twice it's original size and i dispose it immediately for obvious safety reason. The ESC seems to be working but it does not emits anymore initialising sound when the battery is connected. So this makes it impossible to program from the TX in future. Also, when i tested flight later with the same esc, it does not seem to generate constant rpm to the motor. So it's better that i decommission the esc as well.
And now, here's the reason why the plane lost complete power : I bought an Align motor 2 days before I lost my plane. The align motor looks like an inrunner motor but in fact, it is an 'outrunner in a can' motor. Meaning, it is actually an outrunner motor but it is 'housed' in a tin can.
Unfortunately, the so-called 'tin-can cover' was not sealed properly (see pic). It was not a 'screwed on' type but rather looked like it was tight-fit pressed. So during the flight, the cover came loose and popped out from the tin-can. This caused the entire back part of the tin-can to rotate instead, coiling up the motor wires, which in turn coils up the ESC and this effect pulls the esc connector out from the receiver, hence cutting all power to the receiver!
Lessons learnt: Don't buy Align motors!!! Or re-seal the can cover before use!
As the wires to the motor have been coiled up beyond repair, I have disposed it last night. ($69 down the drain...)