Thank you all. I'm starting to accept what has happened. He's still being gelded on Friday, but I no longer cry everytime I feed or water him. Small steps.
A little bit more background that may be helpful to someone in the future. The foal was less than 13" at the withers. As you can see from the picture I'm posting her head was obviously deformed. The length of her head was greater than the length of her neck. Her legs weren't terribly deformed, but not normal either. Her back was rounded or "roached" a bit and probably would have been more pronounced as she aged. I believe she was a Type 3 dwarf which is the most severe that is ever born alive and can sometimes live. When she passed I wish we would have thought about John and his research but it just didn't cross my mind.
As for Corona, I have an email from John Eberth from late 2007 where he says that, to his knowledge (at the time), Sids Husker was not known to have produced a dwarf. Nor was Corona's dam. He states that if Corona ever were to produce one it would be "important." I never asked him what he specifically meant by that.
I've informed John about this, including the dam's info with permission from her owner. We are having blood collected from both Corona and the dam for John to use as he wishes. Not to get too detailed, but we may also be able to still get a tissue sample from the foal, but that's not for sure yet. Sorry if that was too much information.
Here is the only picture I can share of her. The others have the dam and/or other identifying information.