Yes, that's the problem - you have lost your groups, but it didn't happen in UV Mapper because that preserves groups unless you specifically check "Export As A Single Group". It probably happened when you created your new mesh or when exporting from Poser or even when doing the original morphs. So, without the grouping information, Poser will not be able to pose or conform it. If you have MarkDCs Auto Group Editor you may be able to create a new set of groups based on the original jersey. Fortunately there are tutorials around that tell you how to "split" your obj into proper groups, but I can't talk you through that complete process :-( Basically, from where you are right now it would be best to forget the original clothing item and treat it like you have an entirely new clothing mesh which needs to go through the procedure to group it and turn it into a conforming figure. If you look around you will find tutorials on how to do that.