IF that feature were only the parachutes themselves, minus the shroud lines, harnesses, fittings, etc., then I could totally see there being absolutely no trace of them left by the time TIGHAR got the time to poke around down there. Parachutes in Earhart's era were made of silk. I'm not a fiber expert, but I doubt the canopies would have lasted a long time in that rather "active" environment, between the sunlight, intense UV rays, heat, periodic torrential rains, etc.
LTM, who trys to keep his 'chutes dry,
Monty Fowler, TIGHAR No. 2189 CER