Hot, angry heel bulb - abscess? Or ...?

My gelding turned up slightly lame a week ago, and when it didn’t resolve, I called the vet. There was no heat or swelling - he just was short on that hind. He tested negative with hoof testers, and flexions were fine. He walks sound, but trotting and cantering, he’s decidedly off, and more so to the right. The vet’s comment was that the issue was low in the leg, not hock or stifle.

She recommended rest, bute and keeping an eye on it.

Well, yesterday I finally saw a change, when I was cleaning the mud off his feet, he snatched his right foot away as I was gently using the soft side of a jelly scrubber to get his foot clean. Once I had removed the worst of the mud, I felt around, and found a hot, swollen, angry heel bulb.

I hosed off the foot and emailed the pics to my vet, from whom I’m awaiting word. However, for the sake of discussion, here are the pictures. There’s no evidence (that I could see) of external injury to the bulb. What do you think, COTH?

Picture 1
Picture 2

I had a case recently that sounds much the same. Ended up being a piece of wood that ran into the frog and was broken off below the surface. Vet missed it and it caused a nasty abcess in the bulbs.
Wasn’t found until the owner decided the horse needed a trim.
It may be worth a shot to call your farrier to have a look.