most likely just wages owed...you could also try for interest...but to be truthful, I think you may find it very difficult to find someone to represent you...It will most likely cost you more to take it to court than anything you would recover..
and from what I understand of your situation...you really don't have a case for damages. Damages are seldom awarded even in the best case scenario...
I most definitely would not just let it go...demand answers...what happened is not something that an employer can do with out informing you first and giving you the opportunity to decline or accept further employment under the reduced wage...
and I think you are 100 percent correct to keep calm and pursue it in a professional manner......I also would be in touch with corporate daily until you get an answer...