Um... That isn't the WiFi antenna. The wireless antenna is under the logic board. It runs along the inside edge and looks like the 3g antenna. It connects at the top and bottom but can still function with one end connected. Perhaps the bottom cap isn't seated properly? It would explain the symptoms... Also I wouldn't worry about the screws so much. Its such a snug fit that once the flex cables are reattached and the back cover is on nothing can move anyway, plus it will make it easier for you next time you need to have a look or if it gets wet and you need to pull the battery in a hurry. This guide should be taken down. The world is confusing enough... Just saying;)
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