You should still be scouting his main with a wisp or two even after the cheese unless he somehow managed to chase down any "normal" timing scouts you decided to send. And then you would notice a lack of production buildings/moonwells/etc. Now that you've seen it though it will be much less effective in the future.
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Eff_Dee
http://img.imgcake.com/nio/9fdpngys.png