Well, I am a city girl who has many reasons to use duct tape and I do know it will not stick to anything that is wet. How would you wipe off hair enough that the tape would even begin to stay in place with the ends stuck together? It would have slipped and slid all over the place and never held the mandible in place for close to six months under those conditions - and yet it did. Because it was stuck to the hair mass. The hair mass surely would have originally had to be dry to have it stick.
I just tried this when I got out of the shower. No tape on my hair, which an inch or so shorter than Caylee's and no sticky stuff either. just slid right off.
I got a roll of duct tape and then put my head under the faucet. I still have a head of hair. Lightly dried with towel..4 seconds took a 12 inch strip of duct tape and put over my head in tooth ache position and tape adhered to the point it hurt to pull it off.