They have lied to you then.
It definately is a salvation issue to them. here is how they do it if you ask them if sabbath keeping is a requirement to salvation:
"Oh no (smile) we are saved by grace through faith

"
-"Oh ok, thats what I believe too"
-"But if you dont keep God's commandments, are you really, TRULY saved? And we know that the sabbath is one of God's commandments. And God's word is forever"
So it all comes down to keeping the sabbath, you wont make it into heaven if you dont keep the sabbath, you will lose your salvation if you keep doing it.