It might very well be an important part of the puzzle - for LE. Not for the general public. Again, I just can't see any way releasing it to the general public would help find Dylan. It's LE's job to build a case (if one is indeed being built,) not the public's. The public's "job" is to help LE find Dylan. Seeing Dad in Walmart is unlikely to help with that, IMO.
I also have to agree with those who mentioned "divide and conquer." At 13, my boys would take off for the electronics aisle as well. And I can guarantee you that unless we were there specifically to get them something they wanted, they would not look happy to be there, because they wouldn't be. Shopping with parents was never high on their "to do" list. They also would not want to be walking close to Mom or Dad. Definitely not the "cool" thing to do at that age, at least among my three sons and all their friends. Even walking through the parking lot, they were always a good ways ahead of, or behind me at that age.