Similar thing happened to Warrior, Haffyfan. Vet's couldn't find the site of the pus, even though I was adament it was at the point of frog, and decided it could be a fractured pedal bone. X-ray showed nothing so deep seated bruising was the next diagnosis. The next day, I was calling the vet out because Warrior kept going down, laboured breathing, non-weight bearing on the hoof & stood with it buckled right over at the fetlock joint. After a jab of pain killer and antibiotic I was told he may have to go to the vets as it could be an infection of the deep tendons. Next day, different vet came down to jab him again & she had a look at the foot. After much cursing she found the site of the infection, at the point of frog. The difference in him once the pressure was released was amazing & the sense of relief I had was pretty good too!!