Oh no LOL happens to the best of us. It isn't super obvious, but if you put your crosshairs over the animal, it will tell your its status. Helpful when you have both tamed and untamed wolves around. The yellow hearts are a good indication the animal is being tamed, but only if it has recently eaten. Hungry animals will stop acclimating, and so they will no longer have hearts coming out.

I feel your pain, though - I was running to a crypt the other day with my friend behind me, or so I thought - it was a 1 star draugr. "We are here, Lefty! Let's go in and - Holy God! You're not Lefty!"