Sometimes it takes horses some time to warm up to another. I'm sure he'll find someone to buddy up to again.
Logan is a complete recluse with other horses when I put him in new places. I brought him home to two miniature horses... Which he absolutely hated. He now loves the miniature we have left. Probably helps she's a mare... But he's such a reclusive horse when it comes to making new pasture mates. Probably has something to do with him being a barker and not much of a biter when he gets his bluff called :)
Willow - 5 y/o Gypsy/Haflinger Mare
Loki - Yearling Gypsy/Haflinger Colt
Rockstar - Senior Spotted Saddle Horse