If they are your horses, just moved, it is possible they got “kicked” from boarding. This is possible for two main reasons, either inactivity or someone removing stalls from the boarding center your horses were boarded at. It happens from time to time. 

If they are not your horses, it is likely someone is transferring them to you. See if they want them back- I guess? Or you chose what to do with them. 

I think it's boarding facilities changing things up. Thanks! You helped me figure it out!