I was contacted about a month ago from a fellow asking for a quote on a fursuit. The ref art he sent me was this: http://www.furaffinity.net/view/1885394/
I actually know Rave fox (though admittedly, I never knew his real name. I just knew him as Rave), so I assumed he just wanted to get a new fursuit made of his design. I gave him a quote and we communicated some information back and forth. His language and spelling mistakes seemed a little odd at first, then he asked for a shipping estimate to South Carolina (I knew Rave lived in Canada... so that raised some alarms), and then finally he asked if he could get the suit then pay it off after he received it. Since I knew Rave had gotten fursuit commissions before he knew how the TOS worked and would never have asked such a question, so I decided to do some sleuthing.
I contacted Rave through a local furry forum and asked if he got a commission quote from me, to which he replied he did not. From there, I contacted the fellow who commissioned me, and called him on stealing a reference sheet and someone's copyrighted design. He has since gone silent, and I think I scared him off from attempting to get the suit commissioned by any suitmaker by threatening legal action.
Crisis has been averted for the most part, but it does lead to a question...
What if I had not known the art was stolen and made a suit from the provided ref sheet? Although the commissioner who stole the art would be liable for stealing the design, does any responsibility fall on the artist to make sure the design is not a stolen work in the first place?