I think it likely to be a Standardbred brand, which is often on the right side of the neck, but aren't their brands like 2 numbers followed by 2 or 3 letters?
It could be an auction brand. I'm not knowledgeable on such things, but for some reason I thought I had heard somewhere someplace about feedlots branding their horses.
I always thought ranch brands were on the hip/thigh or on the back where the saddle would cover it, so this doesn't seem like a ranch brand to me. Many warm blood associations brand as well, but that is usually a hip brand too, and not a number either.
Think of it not as a failure but as a success in how not to do it.
Don't look in a horses mouth for a gift.