Symbolism, Imagery, Allegory
Remember that foot long, flexible aluminum tube Janie keeps shoving at Hip and leaving in his shoes and food? It shows just how much Gerry's made Hip forget about his past:
It was as if [the tube] were transparent or even invisible to him. (3.6.3)
The more Hip remembers his past, the more he physically grabs onto the tube. He first finds it in the hidden shelter in the woods, and it's the same type of gear he touched on the anti-gravity generator. That's why it's so important to him: it symbolizes his goal. It's his forgotten memory (thanks Gerry) and his goal combined into one object.