@Yoda_LoA: Good question regarding Melissa. Perhaps we'll see her hunting him in future comics?
@thoazol: Look for mirror universe Sigmund to appear in Clint City as part of the Rescue clan in the future. He'll be carrying a cute fluffy bunny instead of a seagull and will frequently be seen organizing charity fundraisers.
It looks like the Sigmund in this comic is the one from the "normal" universe, you can tell by the fact that he is still evil and that he still has the normal GHEIST emblem.
I like this final twist and I hope that this continues to maybe get more clues on how he disappeared.