Is my complaint frivolous or otherwise insubstantial, when applying the motion to dismiss standard of accepting all allegations in the complaint as true and drawing all inferences in favor of the non-moving party?

Whether a district court properly dismissed a complaint against an FBI employee under Rule 12(b)(6) when the complaint alleges Fourth Amendment violations and the defendant's existence is disputed, applying the Ashcroft v. Iqbal plausibility standard and accepting all well-pleaded allegations as true