Non Purchased products in Cart

I need help in setting up zen cart such that if anyone registered, placed an item in the cart but leaves the website and does not purchase, I want the non-purchased item added to the cart be placed back for sale. The way zen cart is now it leaves it in the cart even when a person signs out or leaves the site. I want once the session is over and the person leaves the site that any products placed in the cart be placed back and become available for sale. Thanks !

Zen cart does not remove items from being available until it is sold thru the checkout.
If you selling "one only" type items, then it doesn't matter if many logged in customers have it in their cart.
The first to buy gets the item and if your shop is setup to remove stock, and that items becomes unavailable as a result. It will be removed from the other customers cart at that time.
If a customer is logged out when this happens. They will get a message the next time they login that the item is no longer available