My general point about credit is this: We create no truth, we simply discover it.   Truth is eternal.   Now, to believe that we create truth or own truth is in itself a lie.   

We get credit for speaking the truth or writing about truth or making a movie about truth and rightfully so.   The laborer is worthy of his hire.   

But since truth is eternal and issues from our Creator, it is presumptuous of us to take credit for or take ownership of it.   

Jesus (the Truth) said: " Do unto others as you would have them do unto you."

The shopping cart deal is just a specific instance falling under this rule.   If you were the business owner, would you be OK with people being sloppy with your equipment and parking space?   As a person trying to park in the lot, do you appreciate having to navigate around spaces occupied by carts?   Are you OK with a loose cart suddenly start rolling from a gust of wind and hit your car?   

Giving credit is another aspect of the 'golden rule'.   But not knowing about the history of truth is not a reason to withhold the truth.   

If you live long enough you will hear younger people who heard truths from you, speak those truths back at you not remembering that it was you who first shared the truth with them.   That is OK.   As long as the truth is spoken and written, there is hope for today and tomorrow.