The Loctite Red 271 product page says it requires 260°C or about 500°F.
Henkel (manufacturer of Loctite) has a blog post which says 550°F.
Either way, pretty much permanent for a bike. The LBS obviously doesn't do many fixed gear bikes.

I'd bring the bike back to the LBS and politely ask them to remove the lockring. If it turns out to be Red 271 then I'd politely ask them to replace my wheel and take it from there.


-Tim-