Aww I know exactly how you feel. When we found the tumor on Jada's back, I had a dental done while they had her under anesthesia. She had two loose teeth and one that was rotten in the back of her tiny mouth.
She had quit playing with her favorite toy and her little mouth was staying wet with drool, and I had no idea she was in pain
A week out from her surgery and she was playing again with yellow dog. I felt so guilty that I didn't know she was hurting
I am so glad Gabby is feeling better and don't beat yourself up, my vet said I would have never known about her tooth until it most likely would have abcessed.