The 1st thing to check is to make sure your e mail address for receiving pay pal payments is correct.  You do have a pay pal account, right?   If your e mail for  receiving funds isn't the same as the e mail in your listings, the money may have been "unclaimed" and eventually returned to the buyer through no fault of his own.

NEVER ship an item until you ACTUALLY see the $$ in your pay pal account. 

Do I understand this right??~~The buyer paid but there was a hold on your $$ because you are a new seller.  You shipped the item but the 21 days passed and you didn't inform ebay that the item had arrived and been received by the buyer by giving ebay the tracking/DC number to prove delivery so the $$ were automatically refunded to the buyer??

When you're a new seller and there are holds on your funds from auctions, you need to download the tracking number of the item you sent and inform ebay that the buyer has received his item.  You have to have used DC/tracking to prove delivery.  Once delivery is proven they will release your funds to you. 

You need to read up on the info from ebay on how the holding of funds works for new sellers.  That's the 1st thing you need to do.