If you did not get an email notification nor a record of the transaction in your Account Transaction History, there's two possible reasons. The first would be that system may be a bit slow and the information has not shown up yet. The second and more common one is that you may be dealing with a scammer.
How did you sell the item? Meaning did you provide the buyer with your PayPal Account email address and they used the Send Money feature. Using this method is not recommended as most new PayPal Users usually get scammed. The buyer states they sent the funds and tries to pressure you into shipping ASAP. You then ship and no money is ever received.
In order to protect yourself a better option for selling items is to either have them purchase via a web page which you setup or use the Invoice feature. With either method, they go to the PayPal Checkout Screens, pay, you get a notification both via an email and a record in your Account Transaction History.
Assuming you have verified your account, the funds would be credited to your PayPal Account Balance. Once you have the money, you ship the item. Make sure that you have the tracking information. In addition you can request signature delivery and insure the item if applicable.
