dogs bloody discharge after spaying

Question
My dog is 3 yrs old and I spayed her 3 months ago.  She is utd.  After the surgery, she licked the scar and it opened a little.  I took her back to the vet to have her rechecked and dr. said it was fine. I made sure she had on her cone at all times after that and that she had it on for 10 days. Anyway, I noticed later that she had a lump where the scar was.  I also noticed that a couple of times she has had a reddish brown/yellowish discharge.  It was bad once and now she is okay.  But then it started again.  But it is not as bad as it was last time.  I also noticed that the lump is gone.  I have checked her for it and can't find it.  Anyway, I am going to have her checked out again but was wondering what could be causing the discharge?  Is it possible that the vet inadvertently forgot one of the ovaries?  Someone told me they used to work at a vet clinic and that this has happened before.  Thank you for your advice.

Answer
Wait, where is this discharge coming from- her incision line or her vulva? If it's the incision line on her belly then she probably has a stitch that isn't dissolving.

If if it from her vulva then that is a different story but leaving an ovary is not going to cause a discharge. It would make her act like she is in heat but she would have any discharge if her uterus was removed.

I don't know what utd is. "She is utd."

The vet needs to see her and  he can resolve the issue one way or the other.