Inside the clean sheets. Both the flat and fitted. Although, if your socks are cammo, they won't hide in the sheets.
I could tell ya'all the other places socks hide, but then I can't patent my idea.
5.56mm
What you say is true. The sheets do make for hiding places. Sometimes all the sheets have to be pulled out for inspection. Takes a lot of time. If you have time saving ideas ... those are always helpful. With certain technology in place, as now is, even the worst and best of sock hiders can sometimes be found with an inspection of the sheets. It is an uphill battle but one each of us is improving with time.