Deliberate mistake: If you pay extremely close attention to the scene of all of the Decepticons responding to the small Transformer's message regarding the location of the Allspark, notice that the shot of the police car and the fake helicopter pilot are duplicate shots used earlier in the film.
Deliberate mistake: At the corner of the roof, Sam clutches the statue as he protects the All Spark from Megatron, who then destroys the statue causing Sam to fall. In the overhead shot of Sam falling, as the chopper flies by, we see the All Spark leave Sam's grip and actually fall behind him. Yet, in the next close-up the All Spark is safely held in Sam's arm again. (02:06:50)
Answer: Because the Decepticons didn't know where Megatron ended up for the last 100 years. Bumblebee arrived on Earth as a scout to check out for any clues, found the glasses on Ebay, signalled the other Autobots, which prompted Blackout and Frenzy to investigate the base in Qatar, which lead to Blackout downloading the base computers and Frenzy hacking the computers aboard the aircraft later leading to the discovery of Megatron's whereabouts.
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