marvel cinematic universe - In Age of Ultron, Thor seems to know something he possibly shouldn't?

Sorry for the cryptic title, but I realise the film has only just been released in the UK and Europe and is yet to be released in the US.

I'll hide all substantial parts of my question, just in case. I don't want to spoil anything.

At the end of Age of Ultron, Thor states that 4 infinity stones have now shown up in the last few years.

So,

By my count we have the Tesseract, from several of the first few films. The Aether, from Thor 2. The Chitauri Scepter, again from several films. And finally, we have The Orb, from Guardians.

Now, to my knowledge

Thor, and indeed none of the Avengers, should know about The Orb. I don't remember Thor visiting the Collector between GoTG and the AoU. So, how did Thor know that The Orb had appeared? Or is he referencing a different infinity stone?

I'm looking for an in universe answer, ideally.

Answer

When Thor takes a dip in

the cave water

we briefly see an image of

four Infinity Stones

which suggest that Thor sees that too. For all we know, his actual

vision

contained even more information about the

Mind Stone/Gem/McGuffin

than we actually see.

Also, in the mid-credits scene of Thor: The Dark World

the Warriors Three take the Aether to the Collector.

Therefore they know of the Collector, and thus may well have heard about the events in Guardians of the Galaxy, and passed that knowledge on to Thor. I mean, some big guy blew up the Collector’s home base to steal an orb, and then tried to destroy an entire planet. Word’s gonna get around.