The first one was left in the middle school library. I was attending a long and boring school committee meeting and snuck this card in between two books in the stacks.
Then I thought about adapting the "3 little words" technique from 21 Secrets and started cutting apart an old discarded library book into 3-word chunks of text and then putting them together in different ways. I left this one inside my book when I returned it to the library.
This one was left behind at the gas pump.
Here's a bunch more just waiting to be left....