Yes, I thought same. The laptop body is transporting sound equally to both the mics. And No, I didn't try yet two external mics method.
I was also thinking of trying some other techniques to do this. I was thinking if it is possible to produce a sound using laptop speakers and catch the sound back using laptop microphone if it reflects from any surface like a ultrasonic sensor but without any hardware just using laptop inbuilt stuffs. Can you tell me it is possible to make in processing using minim library or other library.?