Just playing devils advocate here: Greenwald did previously state that he was going to send leaked information to his partner. So his partner isn't just his "loved one" in this. He would be one of the leakers.
Moreover, his partner has a previous history of interest and involvement in his professional affairs.
One of the more hilarious examples: Miranda used to troll for blog posts that were critical of Greenwald and then argue with the bloggers, often posting the same comment (of fawning praise for Greenwald) to multiple blogs. When people realized the comments were coming from Greenwald's IP, it led to accusations of sock puppetry and lots of drama.
Point being, it's reasonable to expect that Miranda's involvement runs deeper than merely being in a relationship with Greenwald. Both past behavior and public comments suggest he might either be involved directly, or he's trying to appear to be involved. (There's a long history of activists inviting law enforcement responses; Rosa Parks didn't keep her seat just because she was tired.)
“When I was in Hong Kong, I spoke to my partner in Rio via Skype and told him I would send an electronic encrypted copy of the documents,” Greenwald said. “I did not end up doing it. Two days later his laptop was stolen from our house and nothing else was taken. Nothing like that has happened before. I am not saying it’s connected to this, but obviously the possibility exists.”
He said he didn't send it but implied he wanted to so it's very reasonable to suspect he did later at some point.
One more reason to suspect the media & equipment taken had nothing valuable on them. I'd assume after one direct hit against ones' person a more careful approach would be indicated. That's still an assumption but I really can't imagine anybody that has been the subject of a targeted theft like that to carry incriminating data on their person across a border.
Lightning doesn't strike twice? It would be silly for the police to have a dont search twice policy, because once such a policy is known, it provides an obvious loophole for people interested in concealing or smuggling items.
No, of course they'd do the search again. But that doesn't mean there was something to be found. Though the fact that he hand carried so many devices including thumb drives suggests that there is a real possibility that he was hand carrying bits. That leaves the question if those bits were valuable, encrypted and whether or not the decryption keys were on his person or kept on either side.
The data and the keys travelling together would be a pretty bad mistake, even knowing the keys would be a bad move.
One of the more hilarious examples: Miranda used to troll for blog posts that were critical of Greenwald and then argue with the bloggers, often posting the same comment (of fawning praise for Greenwald) to multiple blogs. When people realized the comments were coming from Greenwald's IP, it led to accusations of sock puppetry and lots of drama.
Point being, it's reasonable to expect that Miranda's involvement runs deeper than merely being in a relationship with Greenwald. Both past behavior and public comments suggest he might either be involved directly, or he's trying to appear to be involved. (There's a long history of activists inviting law enforcement responses; Rosa Parks didn't keep her seat just because she was tired.)