I purchased a little filly a few years back for 200$ and took care of the mare throughout the pregnancy and nursing (they were in a bad financial place, and I didn't want my filly to have issues with malnutrition right off the bat). When she was 1, they came and took her (they already took their mare back) and told me I owed them 2000$ for her. They took her to an undisclosed location, so I couldn't take her back.
As Cherie said, I was told possession was 9/10 of the law- and since was verbal, I couldn't do much about it. I won the court case (showed vet bills, feed bills, etc) but there was no way to FORCE them to give me my horse back, since they said they wanted to appeal (which they never did) . Took me 2 YEARS (after she was 3) to get her back, and by the time I got her back she was incredibly stunted (she hadn't grown an inch, she was kept in an area the size of an average backyard with 2 other horses, and was just very... Dead in the eyes, so to speak) The only way I got her back (even with winning in court) was I had to figure out where she was being kept, I went over there with a trailer when they weren't there and brought her back. They tried to take me to court for stealing my horse... But, again, possession is 9/10 of the law. I won, but my poor horse didn't.
So, GO GET YOUR HORSE! And get it ASAP by any means necessary!
And never, ever do a verbal agreement again. Done are the days where a hand shake works, there's just too many people you can't trust, even (in my case) people you have known for years.