If you have put your logo on Facebook, then you do not own any right to the image, you signed away those rights by their T&C's
If they have put it on their website you can get in contact with their ISP here is a link to find who is their ISP is.
http://www.domaintools.com/If they have the domain by proxy then you have to contact them through that. But you have to file a cease and distress notice, before any legal action can be taken. You can use the wayback machine to see when they changed the logo.
http://archive.org/web/web.phpI know I had the sane problem, when I had used to sell Diamondback and Ninja's machines someone stole my images which cost a fortune and to top it off they used them as a link to Ashbys, which ticked me off somewhat.
And all images belong to the creator unless they are assigned to you by what ever means. You also can have them protected as SM, which is a service mark.