Hey, My story exactly!!
My stbx (obviously we are not divorced) purchased a home with his g/f in another state. He thought he was protecting that asset by titling it in her name only but the dumba** used the money he took out from our home to purchase it!!!
HAAAAAAA!!!! It is now marital property!!!
Now we haven't had our court date yet, but we have the documentation showing the wire transfer from his account to the titling company to purchase their home (or should I say her home?!!)
So, I will let you know what the judge decides but it is legally marital property!! And I don't stick with one opinion, I have asked now 11 lawyers the same question and all the answers have been basically the same.
It IS marital property and she can be forced to refinance to take out my share or he can be forced to simply come up with the money to pay me back or I may even be able to put a lien on the home!!
I know the g/f is stewing in her juices right now!!!

As the other posters state, DO not put anything in his name, do not have him make any of the down payment so you might as well not even purchase the home.
Sorry!!