Wolves' Hammill, who came off the bench in the last game of his loan spell, struck deep into stoppage time to rescue a point for the struggling Terriers and deny Blues boss Lee Clark a winning return to the John Smith's Stadium.
Grayson said: "I have not spoken to Dean Saunders at Wolves about Adam Hammill yet. I will speak to him after the weekend and see what he wants to do.
"If that is his last action for Huddersfield then it is a brilliant way to go out. He kept the ball alive and had three players around him. It was a fantastic goal.
"We have an honest bunch of players out there. They will make mistakes, but they are honest and will keep working very hard.
"That is another very valuable point for us."
It had looked like a goal in first-half stoppage time from Callum Reilly, his first in senior football, would be enough to give Birmingham all three points.
Chris Burke nearly doubled the visitors' lead when he curled a powerful shot wide on the hour mark.
But the Terriers, who are now without a Championship win in their last 11 outings, came back strongly in the closing stages with Alan Lee and Jermaine Beckford both coming close to equalising.
Hammill then escaped three defenders before firing a curling shot into the top corner from just inside the box to level in the 93rd minute.