I'm sorry this happened to you.
Keep us apprised of the situation.
Nail their arses to the wall!
No if, ands or buts bout it.
Also, don't stop at your local authority level and FBI, be sure to also file with the FTC.
This type of invasion comes under many and varied categories..one of them being identity theft.
IP numbers and more detailed information is available from eBay...however before you can receive this info...file! And Fast!
As you've ascertained, EBAY will require a report to be filed with the local police department and/or FBI before giving these numbers out.