Temp/spare horse vanished

So, i left both my horses at camp to do a mission with Hosea (selling moonshine back the Braithwaites). I had a nap afterwards and when i woke both my horses were gone from camp, and neither icon shows up. Whistling got me my main horse, but there is no icon for my spare. Should i assume that for some reason its vanished? There were very few camp horse present at all tbh. Only about two.
I have not bonded or even interacted with, another horse. I just rode a wagon and gave out free drinks.
Whistling does nothing.