I guess they're making up for a looong molt/break in laying. I don't see how they could have hidden the eggs - it is a small raised coop and I look through the 1" of litter daily because I have one that refuses to lay in the nest box. It's possible that they both layed in the afternoon after I looked on Saturday but still 7 eggs in 2 days from 2 hens?!
My first thought was an early April Fools joke too so I went inside and asked the family if they were playing tricks on me! They didn't know what I was talking about but I'm afraid I've given them an idea as one response was: "Oh, I never thought of putting eggs back outside . . ."