Punch cards were not that hard to sort after dropping them.
Once you have a deck, draw some thing on the deck edges with a permanent marker making sure that all the card edges have been marked.
If the deck is dropped, first of all it doesn't usually scatter that much (cards tend to stick to neighbor) and the marks on the edge help visually sort the deck pretty fast.
Actually punch cards could have indexes. Several programming languages did not not use the last columns of the cards and reserved them for a number which could be used by card sorting machines.
Punch cards were generally created by hand so the ability to cut and paste new punch cards was considered a significant advantage. This on the other hand is created by a computer and not human readable so a simple index is easy enough to add.
Then again, punch cards didn't.