On a new playthrough I came across a horse (unowned) there was no "steal" flag. I rode that horse and Convenient Horses allowed me to access the inventory, on my way fighting through enemies I stored some loot on my horse's inventory. So I rode going to Morthal and went to the Thuurmagist's hut to unload and sell, I got a message from convenient horses right after selling the items that "Horse inventory has been transfered to my char". When I went out I didn't my horse and found a dead frostbite spider.. I used "Whistle for horse" from CH and got a message "You must own a horse".
Anyone know what could cause this?