if you contact the seller telling him it's yours, you are giving him a warning essentially to pull it from ebay and cover his tracks. Use your knowledge to your advantage. You don’t catch a criminal by emailing him that you are onto him
Ebay selling my missing amplifier
8 months ago I sent an amplifier to europe for upgrades. The amp went missing and there were investigations that went unresolved. I happened to be searching on ebay and noticed the amp and when I magnified it Bingo the serial number was same. It is an ebay seller store that is listing it. Ebay has not yet responded after several attempts. What next?