Have you ever found a slot ticket left in a slot machine? It just sits there in the printer slot after the previous player forgot to take it out and left it there. If it is for a small amount, there really is no concern, however larger amounts present an issue for many people. Even small amounts sometimes are challenged by the previous players when the eventually realize that they forgot to collect their slot tickets.
Every slot ticket has a serial number. They are date stamped, time-stamped and stamped with the machine they were removed from. They contain a lot of information and are easily traceable.
It is just not worth it to keep the ticket and play it or cash it. A small amount of money is not worth the embarrassment of a public confrontation or being accosted by security.
When a ticket is forgotten and the player comes back to collect it, they have several options. They can ask for the ticket and if refused, can also call security. Security can checked the videos to confirm who removed the ticket. If necessary track them through the casino and challenge them for the ticket.
This actually happened to a friend of ours. She waited over half an hour to see if the previous player was going to come back. They did not so she put the ticket in her purse and walked away to another slot machine. Security eventually caught up with her and demanded the ticket back.
Fortunately, she still had the ticket and provided it to security. Otherwise, she would have had to come up with the cash and return it to the original player. They had tracked her through the casino and easily found her to confront her about the lost slot ticket.
The moral of the story is that you should not spend it. If it is truly a large amount, call security immediately and report the situation.