In most state legislatures (although not in all, and not in Congress), a bill is filed by a specific senator or representative, and any amendments to that bill must be offered by a specific individual, either the author or a different senator or representative.

In such a case, it's easy to pinpoint the legislator responsible, but since most elected officials couldn't write their way out of a wet paper bag, undoubtedly the amendment was drafted by someone in the industry and handed over as "this is the language we want". In turn, the legislator would have turned it over to a staff person to type up, and he would have presented the amendment quickly in passing as "this is clean-up language to fix some problems with the UCC."

Getting the legislator to point a finger at the lobbyist(s) who pushed the amendment on him, however, may or may not be easy. Sometimes they'll turn and make it public, out of embarrassment, as a way to show up the lobbyist. Other times, they'll keep quiet, and out of gratitude the lobbyist shells out another campaign contribution.

I will say, though, I've seen legislatures rush to un-do something like this when they feel like they've been swindled. It depends on how much public outcry there is. Unfortunately, there's often not enough over UCC-related stuff, like this and UCITA, to generate a response.