There are hundreds of cards under auction at the same time, and since only 50 cards are shown in Fort Worth at once, the default view shows auctions ending soonest, not auctions just recently listed. Players CAN see your card under auction, but they'll need to use the correct sorting/searching parameters in order to do so.
Players can search for any card under auction by using the Auction Search feature at the top right of the screen in the auction markets (Fort Worth and Moscow).
You can search for a particular card, or sort auctions by price, when they're ending, when they were posted, if it's an active or retired collection, and who is offering the card.
To confirm that your card is indeed under auction, you just need to go to the auction house, click the list icon, and where it says 'Offered By,' click 'Me.'
Many players who are auctioning a card will also post in the PackRat Facebook Group that they have a particular card under auction; that way if someone is looking for that card, they'll know it's in the auction house and is just a matter of sorting the cards to show it.