Moltherion

"and will be available on GOG soon."

https://forums.obsidian.net/blog/7/entry-179-patch-notes-103/ Fixed stats issue with saving and loading on the same map where a companion is found. This is a retroactive fix and will restore companions and characters to the proper state. Ranger Animal Companions should not disappear anymore and broken animals will be restored after loading and saving the game. Changed bad data in ranger summons. Looks like fixed.

I've loaded my manuel save and it's ok for now. But lost 4 hours..

Same here. My wolf companion disappeared at Caed Nua Level 4. I can't continue because "You must gather your party before venturing forth." Please hotfix it asap. Edit: Its getting worse... I'm off. Do not try to continue if you have this issue. http://i.imgur.com/7IEnWPj.jpg