Robots?! Well now you're just being ridiculous...
I'm clinging to an interview I read some time ago (which, of course I have only vague details of so I wouldn't know where to find it fory ou) where one of the producers/writers/whatever said that everything on the island had a rational and logical explanation. Fake-o plane crash sounds a lot more rational than a parallel dimension. At least for now.
As far as the wreckage, if there were no bodies found perhaps some family members (especially those with a sizeable amount of coin to blow, i.e., Penny) would continue searching and digging deeper. Throwing a corpse or two in among the metal bits would create a more convincing scene and hopefully send them on their way. If indeed this was created by the mysterious Dharma people, who seem to be of unlimited funds and willing to do whatever it takes to protect their little island there, this kind of attention to detail would be included in their fiendish plot.
(I love saying "fiendish plot".)
Plus, I love a good conspiracy.
To tell you the truth -- I'm leaning more towards the side of my other wacko theory than this one. Never underestimate the fieeeeeeendish plots of those with obscene amounts of money.