There's nothing you can do other than contact the police about it but I'm guessing you won't want to do that either. I'm sure there will be lots of legitimate funds caught up in the confiscation but they probably don't care. Either way they only thing you will be able to do is lodge a complaint with the feds and if that's something you can't do then you're probably SOL.
Actually this is my first time seeing someone said he lost coins due to the seizure of ChipMixer. I was really telling my friend days ago the advantage of mixers over exchanges even if they don't serve the same purpose.
I was telling him assuming it was an exchange that was siezed, people by now would have been crying of fund lost.
Just few hours after the discussion and praises, I have seen one case of coin confiscation.
Op, I don't think there is a very big efforts you can make. You paid the price for privacy.