In Character: "Quick!" says Hunter hoping that does closest does 'something'! Failing that Hunter takes a torch and attempts to burn a portion of the sheet not near the bugbear's skin in the hope the heat / burn will cause a release.
Jonathon would take a knife and try to cut at another part of the sheet away from the torch, hoping that perhaps both their efforts would help the bugbear as he says in a calm yet assertive voice, "It's fine, don't freak out, we will get you out of there."
The Storyteller would also look up, wondering where the sheet came from and what set it off. The tile did seem solid enough but perhaps given the bugbear's size it still set something off.
Drethen draws his sword and cuts at the sheet to free the bugbear. "Be on the lookout for more sheets. I believe this is a type of a monster that will act like a floor or a ceiling to attack." Drethen will hope to cut the bugbear out.
Drethen's words reminds Hunter to also look above him. He keeps the torch raised in the air so if something drops it will get burned.
Once the party get's close enough and starts to try to pull the blanket off of the bugbear, you realize that it is indeed some kind of creature that is suffocating the bugbear. Drethen's attack appears to damage the creature while the other two bugbears also attack it.
Jess fires off two arrows. While the creature seems to have taken a fair amount of damage, it doesn't seem like it's about to let go of its prize.
Out of Character: : Since a To Hit wasn't rolled, the assumption was that Hunter tried to casually to burn the creature. So, no hit, no damage.
Drethen will keep working on attacking the sheet creature to kill it and rescue the bugbear.
Out of Character: Since the creature is not trying to escape and it is not actively avoiding the attacks would it be safe to say we all get +4 to our attack rolls?