Must have taken a little while before you quit stomping around on the left floorboard looking for the gear shift pedal too..

 

Yes for a while I would back off the throttle while trying to pull in the clutch using the brake and my left foot groping around to change down.

 

I never had one of my sleds thumb throttles freeze if parked outside even parked uncovered under 2ft of snow. I quess that's why snowmachines only use thumb throttles 100%.

I left a Street bike out all winter "covered" and tried to start it and the throttle would not snap back on its own. There is just to much contact surface area between the twist grip and bar for moisture to get in behind and freeze.
The throttle cable was sure not what was freezing up.

ATVs have snowmobile type throttle because some people actually use their ATV for ice fishing around here.

 

I live in western New York, been riding here almost 30 years. I have had numerous atv thumb throttles freeze and stick. I never got into sleds much, but I have a feeling they are better protected from the elements than many atv throttles. Doesn't sound like an issue for the op.

On a side note, I run throttle extenders on my race machines. Moose makes a fairly cheap bolt on model that should work. I have used it and while it looks a little clunky, works fine.