*Fingers, toes, legs and eyes crossed for you! I can sadly relate to the worries of this happening to you and your beloved horse... and even though I can't help....I can send you virtual (((well-wishes)))
I'm sorry to hear that, Phoenix :/ Lameness issues suck, especially those not easily diagnosed. Sounds maybe a bit like ringbone? I'd definitely consider a second opinion! Hope it's something easily fixable and she recovers quickly.
So I finally have answers! She has indeed caused trauma to the Pastern bone, not the coffin bone, and it has become inflamed and irritated underneath the connective tissue. With steroids this spot should heal within the next 3-4 weeks. If it doesn’t we have a plan to get more aggressive. I was warned this is something we have to fix or else it has the potential for turning into ring bone. The spot on the coffin bone that showed up on the other vet’s x-rays looks to be something developmental and shouldn’t cause her any issues.
The vet is very optimistic that she should be sound within the next 3-4 weeks however. :)