Without opening the packs, it has to be very hard in most cases to "search" packs. I can understand cards that make packs significantly thicker or if there was a way to detect certain cards, for example those containing a metal hat was magnetic, significant enough weight differences, etc.
However, I still strongly believe that it is the responsibility of the card makers to combat this. NOBODY ELSE WILL. We know there are dishonest people in the world and being naive enough to believe that wouldn't extend to locating valuable cards in packs is crazy. Making a special card SO OBVIOUS in a pack compared to another pack is irresponsible, knowing many of the boxes sold are packed out. A lot of special products have or have had special packs or cards, like case exclusives, bonus packs marked as such, etc. That is fine, because it is marketed as a special pack and only available by buying the box/case. If someone buys a box/case and decides to sell their "hot" pack as a mystery break, that is one thing, but to make it so easy that people can find and advertise otherwise normal packs containing hits is defeating the purpose of random insertion...SOMETHING THESE CARD MAKERS INTRODUCED TO US AND HOOKED US ON WITH INSERTS IN THE FIRST PLACE!!! There is an answer to making these special cards detectible. Not sure what it is, but the manufacturers need to make it impossible!