Yes, I have had this issue on my S3, S4 and Note 2. I carry two phones and usually put the one Android phone (Note 2 or S4 now) face toward my leg.
I have pulled the phone out of my pocket in the phone app, as well as internet browser or even the app store. Usually apps in the quick access bar.
I can usually tell when it happens a lot because I can feel the heat from the phone on my leg, as well as when I take it out of my pocket.
Both my Note 2 and S4 have slim cases on them and the home button sits about flush with the lip of the case making it just as easy to accidently press it.
I have the phones set for screen swype, but may have to change that as I think the friction against the pocket fabric is what is causing the screen to unlock.
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