Secret Throw Up

This is a funny.  The other day I was working with students at my reading table.  A little boy comes up to me and says, "Ms. Coleman, I threw up."  I asked him where since I had not seen him or heard of chorus of eight year olds saying "EWW! Yuck!"  He said in the classroom but I cleaned it up.  Now my classroom is tiny so I see and hear just about everything!  I asked him who saw him throw up (and so kindly clean it up).  He tells me no one saw it.  I said, "So you threw up, cleaned it up, and no one saw it?"  He said yes.  So I said ok, go to the nurse.  He, of course, was fine and spent the rest of the day at school.  Do they think I am that stupid or do they simply think they are that clever?