There is no "evidence"; by any reasonable interpretation of that word there would have to be an actual accusation of crime for there to be evidence of one. This was a search predicated on literally no actual basis apart from "we have the right to search your device because we have ultimate power at border passings", essentially just a fishing expedition.

This also doesn't even get to the more important point: If you don't have the contents of the phone you have literally no evidence of a crime being committed, other than the one they invented post-facto: "Deleting data that could hypothetically be incriminating, not in any specific way but just generally, maybe".

> if anything

That’s the crux of the matter, isn’t it? If there was no suspicion whatsoever, hence no investigation, then he couldn’t possibly obstruct it.