Two things may happen. First, and the more likely event, is that you will pay the pre-stock dividend price and when the payment date comes you will be credited with the additional shares. Sometimes an individual sells a stock between the record date and payment date. Several days after the payment date they receive the additional stock certificates in the mail. What will always happen is that they will receive a call from the compliance department or sometimes their broker, and will be told to mail back the certificates.
Some individuals are insistent that they are owed the stock.
If this happens the brokerage firm won't argue. They will simply tell the individual that they are canceling the certificate numbers and to use the stock as wallpaper. That's all it's good for. Stock dividends and splits generally don't show up on price charts. The reason for this is that it would be very difficult for anyone to analyze the chart with large gaps appearing when the stock split.