That's not how the law works. In fact, that's intentionally not how the law works specifically because of what you said. They don't have to "identify the evidence" that was deleted; they need to show that records were destroyed knowingly and intentionally which the government intended to and had the lawful authority to seize – namely and quite broadly the contents of his phone, which he obviously, knowingly did. In fact, this is so not-how-the-law-works by design that the US legal system uses the common law concept of adverse inference for cases when evidence is withheld or destroyed.
If the federal government shows up to search my house and I burn my house down, the point isn't "well show me what evidence I destroyed lol". This is borderline SovCit pseudolegal logic.
Here's the statute he was charged under.
As I noted in another comment, it's likely the "lawful authority" of the government to have performed the search in the first place will be challenged, which is what the statute requires in part (a). It'll be up to the government to show they had this authority – which it seems like they didn't, and I hope it gets thrown out, but regardless, your interpretation of this is abject nonsense.
TL;DR: They do not need to know a single byte of information that was on his phone for this charge provided they can show they had lawful authority to seize it.