No one here can tell you this and if the email you received did not explain why your listing was removed contact eBay Customer Services, not sure if they will be able to see the reason, but worth a shot.
Perhaps the word ' bone' had the bots thinking and linking bone / ivory ?
All I can confirm with you is, if it has been removed with no instruction as to how to change the item to allow relisting, then do not relist the item, you may receive a restriction on your selling account if you do.
To Contact Customer Services it's a Live Chat, or you can select to speak and request a Call Back. Click on this link:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On weekdays lines open between 8 a.m. and 10 .m.
On weekends they open between 9 a.m. and 6 p.m.
