Lin Yifan and his companions didn't have the scent of the three large spiders on them, so the only "tracking device" might just be that Sun Fruit.
The Sun Fruit had been climbed over by the three large spiders for a long time, and it was bound to have chemical signatures left by them; so the three large spiders were able to locate them at all times, akin to a positioning system.
After identifying the culprit, Lin Yifan immediately asked Long Tengyu to give him the Sun Fruit.
Long Tengyu didn't know why Lin Yifan suddenly wanted the Sun Fruit, but since Brother Lin instructed it, there must be a reason, so he did as told.
He then handed the Sun Fruit over to Lin Yifan.
After getting hold of the Sun Fruit, Lin Yifan pretended to put it in his trouser pocket, but it was actually a diversion.
The real place he stored the Sun Fruit was in his blue Immortal Ring.
