Thor is absolutely assuming Loki is responsible for her shift in attitude. He has that effect on people, after all, and the news he's brought isn't exactly cheerful. Nervousness is probably the most appropriate reaction she could have, honestly. If even Asgardians have reason to fear Thanos, humans won't stand a chance.

No matter the motives for Loki's question about the ring, Thor's glad it's destroyed. There are already enough powerful magical artifacts running wild out there without some complete unknown that might fall into the Mad Titan's lap. (Or Loki's.) Just the Infinity Stones alone are bad enough.

"Two of him," Thor repeats, and gives Loki a speculative look. It wouldn't be the first time his brother's chosen to wear that particular face, and here especially, it might go unnoticed. But... no, for all that Loki is an excellent liesmith, Thor can't detect any sign that he's to blame for this particular sighting. Still, it might be worth working out some kind of passcode system, like Stark has pushed for in the past. Just in case.