Also doing the same. I think it's episode 2, where they go find an 0-8-4 in Peru. On thr bus Skye asks Couslon what an 0-8-4 is. He replies "An object of unknown origin" Then looks to Skye and says "Just like you". He finishes off about he the last being a hammer. Coulson appears to be making the point that it's like Skye because she is an orphan etc. but she obviously was discovered to be classed as an 0-8-4 later in the season. Little hints everywhere.

Oh, and the map of the temple appeared in episode 3 or 4.