Basically after falling through the mast you're faced with a restricted arena with two (I believe) golden fists which need to be shot at the Grolgoth's arms. You have to be very careful not to crash into a wall or steer into the lava (which is rising constantly) else the battle restarts.
So I'd describe you this fight. There is a falling cutscene, then you fly on shell and try to collect something that indeed looks like Golden Fist, but without Golden Fist (only sparkles). It appears in one of two corridors. Ater some shooting into G's arms and eventually into it when it is in lava (it causes faster shrinking of his life gauge) it starts to shoot homing missiles and make lava rising (but then, it goes down; also note that Razor makes him jumping higher to avoid lava).
The glitch is apparently, if you hold down X and O while flying into the ceiling, you get to go in a secret passage which gives you a green sparkle. Grab that and you have infinite ammunition when you grab a sparkle.
...err... it sounds as this unlimited ammo secret, just with these X and O! So maybe that's why some people claim it appears! A question: what does they do normally? Jump and shoot?