Garland gave Vancouver a 1-0 lead at 1:57 of the first period on a one-timer from the high slot after taking Teddy Blueger's pass from the right corner.
"We give up one goal, it's not a big deal, we keep playing and keep playing our way," Buchnevich said.
Parayko tied it 1-1 at 4:22 of the second period after taking a pass from Thomas and beating Demko with a wrist shot from the right circle.
"I'm just trying to find spots in the [offensive] zone and find holes that I can kind of jump into," Parayko said. "I think the forwards have done a great job of kind of finding us [defensemen]. It's been good, I guess, that way."
Brock Boeser, Nils Hoglander and Elias Pettersson all had high-danger chances for Vancouver in the third period prior to Thomas putting St. Louis ahead.
"Obviously disappointed, 1-1 going into the third, you want to find a way to get points out of that," Canucks captain Quinn Hughes said. “But we had some hard looks, just didn't capitalize and execute a little bit better."
NOTES: Thomas earned his first NHL All-Star selection; Hughes earned his second. … Thomas has nine points (four goals, five assists) over his past six games. ... Hughes had a five-game point streak (one goal, six assists) end. ... Parayko played his 614th NHL game to tie Barclay Plager for fourth place among Blues defensemen for games played in their history. ... Blueger has 10 points (three goals, seven assists) the past nine games. ... Perunovich has five assists in his past five games.