I'm a bit late to the party, but glad you got it sorted.
I'd probably resort to the same methods mentioned above, after trying to lever it out with a pair of sidecutters or pincers. These having a sharp edge will get a hold of the key pretty well. Normally, once you get it on the move it's a done deal.
Obviously would recommend using an old pair of cutters, not you're best ones for this job, but as long as they are reasonably sharp.