Mouth Problems

I posted before that I was going through some force fetch issues with my 11 month old Billy. We seem to have gotten over the hump with that and we have moved on. Yesterday shooting some BB marks the first bumper was brought back properly and held, on the second mark we run he goes back to grabbing the bumper, in this case a standard BB bumper, by the cord. Now he made a concious effort to grab it there. I thought here we go again but on closer inspection saw that he had blood on the bumper and his tounge. He did this once before and I took him to the Vet to see if we had a tooth or gum issue but while the Vet said she didn't see any problems he was also moving around quite a bit and I'm not realy sure she got as good a look as she should have had. He's to old to be teething so I'm wondering if anyone else may have experienced this and if so what was it or what was the cause? This seems to happen with hard bumpers the issue dosen't seem to present itself with softer bumpers.
Any thoughts?

Mac