To locate our "Buyback" feature, simply click on a vendor, click the "Sell" tab, and you will see "Buyback" towards the bottom of the window. Using this button will restore recently sold items, it will also deduct the amount of PAX Romana you sold it for.
Check here for any lost items you think you may have deleted while having a vendor window open first before placing a petition, if you still need assistance, and you have not had a item restored on your character in 30 days, a GM will be more than happy to assist.