Purple Salvage / Confused

ok Been reading posts and most the time I know when to Salvage and what to salvage but I've had a couple of items I've salvaged that confuse me a bit.

I recently had a purple item I grabbed from one of the missions, identified it and it was an item unlock of some kind of bow string (I think that's what it was). From there I used an Expert Salvage kit on it and got ... 2 Tanned hide squares?

Salvaging an item for a rune or upgrade item is hit or miss. sometimes you will get the item and other times it will fail and you get the regular crap.

I found a rune in an unidentified dropped salvage item, and accidentally used a regular salvage kit on it. I was a bit annoyed, but it was for a mesmer anyway and I didn't have that as a profession.