I don’t know if this has been covered, but for suspicion of what crime did they originally detain you in order to discover that you were recording them? Under the rules of Terry, you were seized if you felt obligated to remain with the officer. For the seizure to be legal they had to be able to articulate a crime they suspected you of committing and that your seizure was necessary to the investigation. If the original seizure was illegal, then they have nothing on you even if it is illegal to record them without their knowledge. After all, you wouldn’t have been recording them had they not detained you.
They cannot claim that they saw you recording and detained you for that, they already admitted they didn’t know you were. (If they did know then there was no crime anyway) They cannot say you weren’t seized if you felt, and any reasonable person would have felt, obligated to remain.
It just seems to me like there was a big gap in my understanding of what happened to you. You were kicked off the Metro, then you were speaking to the police, then they arrested you for wiretapping. The gap is at the point that they were talking to you. What crime were they investigating that legally allowed them to detain you?