It would be a more certain bet that they’ve done this with the AT&T surveillance than putting money in any cryptocurrency.
Even knowing that parallel construction exists, it's still pretty shocking to see it used in practice.
eg I'm aware of a case here in Seattle where the Seattle PD coordinated with the feds to use a Stingray in the arrest of a fugitive. They thought they knew exactly where he was, and just used the Stingray to confirm his location before using a cooperating informant to lure him out of the building.
The police report of the incident has all of the officers creatively neglecting to write the full truth of how the arrest occurred, not a peep about the Stingray at all.
The biggest issue, in a sense, isn't that defense attorneys aren't able to challenge these devices use, but that prosecutors are not slamming law enforcement for unlawful use. They aren't incentivized to in any way except by meing a radical proponent for judicial as systemic integrity. Such a personality characteristiv is not going to endear one sufficiently to law enforcement enough to likely even be informed that a case may have had less-than-legal investigatory methods employed.
Literally the only realistic way to catch these types of abuses is to essentially assume they happen, and dedicate adversarial resources with relative-to-Law-Enforcement level privileged access to the means to investigate law enforcers.
I.e. Internal Affairs/an Inspector General like construct.
In practice, however, any system that implements such a thing still has levers that can be applied to sufficiently frustrate the efforts of said groups to render it of questionable efficacy.