That happened to me once. Changing areas fixed it.

I use Toybox to remove then add the Saddle up feat on whoever has him, works most of the time

i got him permanently attatched to my main character... even after removing the statue. i can summon 2 bismuths at the same time, but can only ride one. any other character trying to summon him simply doesn't get the saddle up ability in their list. remounting the statue on my main character and using it again and/or removing it from my inventory doesn't remove him. character respec does remove him. not that i want to. i have him equipped and still have all my belt slots. it's a lucky glitch, unless i were to acquire a pet through my class, in which case, it simply doesn't spawn. i experimented with my additional 20 levels when i went legendary.