It’s a press fit, more than likely it just spit the wheel off. Best remedy for that fix is to simply reattach it with some Loctite shaft lock. 680, 640, or equivalent. Carefully take the truck apart, get the side frame out of the way, CLEAN YOUR PARTS!! And then apply the loctite compound to the wheel only, and push it back on till it sits where it was. Be mindful of the spur gear arrangement as you lower that geared wheel back towards the others,….check your gauging vs. the other axle set, and let the loctite cure for a while, …overnight is best …
Pat