I'd not be surprised if it wasn't a reskinned gelatinous cube and was in fact an actual Living Spell.
Somebody must have gotten the adventure to verify - fwiw, if the creature _restrains_ then forced movement (like a bard's slide) would not bring you out. I imagine you'd remember if it restrained, since that gives -2 to attacks and you give combat advantage...
Otherwise, if it 'grabbed' and didn't have something special, yeah, the DM called it wrong. If I used Divine Call on my invoker to pull an ally three squares with a word of divine power... oh yeah I'd expect it to pull him out of a gelatinous cube all right.
Now, the pushing Gelatinous Cube thing is actually a somewhat different issue. The grabbed target is 'in its space' and it moves normally with creatures engulfed within it - I wouldn't call out a DM for ruling as such, even if I'd default to the way that favored the characters being able to rescue their companions.