How can I tell if the LFS sold me DEAD Live Rock?

I forgot to add that there is not one sign of any life whatsoever on this
live rock .. nothing moves, no critters, worms, etc .. nothing .... and I
even have been looking at the rock with a magnifiying glass just to be
sure......I do notice some " mini tentacles" but I think they are showing up
now simply because my new, fresh crushed coral is so fine that there is a
"dusting" of coral that gets stirred up by the fish and this must be
sticking to the old, dead algae on the rock... I'm not sure .. but that's
what it looks like. Again .. sending someone a couple of pics would ease my
mind.

Caper