What was it? If a Prohibited Item EBay would have Removed it. You can Claim through PayPal if you Paid that way. Log in and find Resolve a problem down the left hand side. Open a Case for Item Not Received after 7 days just in case it does turn up?
Add in the Notes that Ebay have Removed the Item. Escalate the Case after 2 days but before 20 days.
