Deleted files keep appearing

I am using a Micro SD card in the card reader of my 2013 VW Gol to listen to audiobooks downloaded on a Macpro computer.  Yesterday I put the card in the computer, erased all the files, emptied the trashcan on the computer, downloaded 6 more books, and transfered them to the card.

When I put the card in the car again, the 4 original books show up on the screen but not the new ones. All the books play normally. So today I put the card into the computer and the original books do not show in the files list, but the new ones do.

I checked the file info and the number of files and the capacity matches with the 6 new books I downloaded so the 4 previous books are not on the card.

So what is going on? I have been using this card the same way for 9 months with no problems. 

Did you empty your Trash while the player was still connected?