Im no mechanic so Im only offering this in speculation.
You've just landed on an island. You've, theoretically, have spent several days crying out to thin air, growing more and more desperate each day. Each sunset, your hope of quick rescue slips further and further away. Hypothetically, you dumped most, if not all, of your emergency equipment for the sake of weight back in New Guinea or before that. Now you are on an uninhabited island, without readily available food, water, shelter, etc, with little more than a makeup case, the clothes on your back, and whatever you can salvage from the airplane.
So the tide is threatening to take the plane over the edge. You know that a patch was placed over a window. Its riveted but unlike the rest of the airplane, it is installed after the fact and possibly weaker than the surrounding structure. You have no cooking surface/water collection device/ material for weapons against mutant crabs etc. You're terrified, hungry, thirsty, frightened, desperate, hurting, regretful and all feelings in between. You arent likely to have much luck disassembling an Electra, teetering on a reef, without an impressive array of tools....but there is that patch. Now, it is a long shot and this is purely speculation, but if someone is desperate enough, the body can achieve superhuman feats. We have documented accounts of it. I can even offer my own.
When I was 14, we had a gas explosion that trapped my brother in our garage (It was walled off inside for use as my dads work shop) . My brother was burned 70% of his body. After my dad literally ripped the side door off its hinges to rescue him, I realized that his work truck was parked in the driveway, practically against a house that was burning down. Without it, my dad couldnt work. Without help or anyone telling me to, I jumped in, put it in neutral and pushed it up our driveway from the drivers side door, to get it away from the house. A scrawny 14 year old pushed a 1 1/2 ton flatbed truck up an incline, 20 feet. I barely remember it. I was 5'9 and weighed all of maybe 125 lbs at the time. But I had just seen my brother covered in 3rd degree burns, my mom screaming, my home on fire, and my dad dragging a garden hose around to put my little brother out....I was helpless, terrified, and saw something, ANYTHING I could do. Its a true story and printed in the December 13th, 1996 St. Louis Post dispatch if you care to look it up.
The point Im making is that it may seem impossible to "kick out the patch"...but if desperation is getting the better of you, you'd be surprised what you are capable of. So maybe she/he/both of them knew that they needed to salvage what they could of the Electra and did whatever they had to. We still cant be certain what, if any, tools they had on board but it offers just one more theory.
Or maybe its just a random piece of aircraft aluminum that washed ashore from an offshore wreck. We wont know until we know.
Krystal "Still sleeps with a fire extinguisher in her bedroom" McGinty