That's my point. If you have your laptop locked depending on whether they are close by or not, then throwing the key away will not help you.

I was trying to say that it seems to me as an ineffective method. Just as ineffective as trying to argue with the police that since you don't have the drugs on you (because you just tossed them) you are not in trouble. The drugs don't disappear just as the keys won't, so the agents would just have to get the keys and unlock your laptop.