I could swear there was a trait, or feat, or something I saw once and can't find again. Maybe one of you will remember what it is called.
The gist of it was that you have a horse you are bonded to. You could leave on it's own, and could call for it any time. It would show up within a certain amount of time.
The Blood Steed trait is probably what you're thinking of.
I don't have Varisia: Birthplace of Legend, but the Blood Steed trait is exactly what I was thinking of. Thank you. In a recent KM game, we had four horses outfitted with Horseshoes of Speed. They were often left outside while we explored dungeons, etc. When one day we emerged after a couple nights and they were gone. It took some time to replace the magic horseshoes. Now we hire attendants for the horses when we know a dungeon crawl or whatnnot is coming up.
Sadly no. We were far outside our kingdom, and I imagine somewhere far away plainsmen will talk for years about the horses they could never catch, and years further some low level adventurers will find a set in a pile of bones. We had to wait months to track down another four sets.