In a multi-sig transaction, if one party refuses to sign, what happens to coins? Are the coins forever lost, or is the transaction voided as if it never was attempted?
It sounds like those two scenarios are the same thing.
If a transaction output requires two signatures to be spent, but one is never available, then the coins on that output aren't going to go anywhere. This is just like where a transaction output only requires a single signature, but it isn't available.
However, this all depends on what type of multisig. For example, if it's a 2-of-3 and one party refuses to sign, then the other two can spend the coins. If it's a 2-of-2, then the coins are stuck.