Guild Wars 2

This has happened more than once, I got a key for the black lion chest when I completed an section map, but when I click take all it doesn’t show up in my inventory. I now have 4 chests and no way to open them.

Does it appear when you re-log?

There was a glitch in beta (and a guildmate experienced it once in live) where sometimes you would get an item and it would be invisible in your inventory. A re-log would make it appear. That may or may not be the case here.