The Scotland stand-off received a heavy blow to his head while attempting to tackle Scarlets' Vaea Fifita. Hastings received medical treatment on the pitch but was able to walk off.
In today's edition of The Scotsman, Smith said: "The dark side is the injury to Adam. That's bad. He's gone to the hospital to get sorted out. I don't want to go into the medical side of things but he looked positive. The fact that he got up and walked off was positive, but obviously he's going to be checked out in the hospital and X-rayed.
"We hope and pray that it's not that serious. I thought he had his head on the wrong side of that tackle. Maybe a little technical error, but sometimes at a professional level, the guys get it wrong. I don't think there was any menace [from Fifita]."
Smith also had praise for his inexperienced team who had to grind out the victory over Scarlets. It was an mistake-strewn performance from the makeshift Warriors team but Smith was pleased with the way debutants Fin Richardson and Jare Oguntibeju and others performed against a strong Scarlets side.
He added: "I'm really proud of that. Some of these players that played tonight would have not been in the [URC] final at Loftus. They would not have been in the pictures and everything that was done.
"But they merit a medal tonight because they stepped up to the plate. They kept working hard. To look these boys in the eyes in my office or down here when they work hard [is a great feeling].
"It's good for them to be rewarded against a full-scaled side that was well-drilled and well-planned. They kept us out when we needed to score. Compliments to that."