Plot wrap-up question

*** Spoiler Alert ***
I couldn't figure out how [spoiler]Igor, the ballet master was completely cleared at the end? There was a conversation between him and Sandra earlier in the film where he said something like "You think Blackie knows we're in on this?", which I think meant the stealing of the necklace, and yet at the end he gets off and is going to marry Joan. Wasn't he [/spoiler]part of the gang and guilty too?