Where is the release button for the gas cap on a 2004 Mazda MazdaSpeed MX-5 located?
I believe it's in the center console.
Mark is correct the center console houses the trunk and fuel lid release.
Also on a side note Miata.net has tons of helpful info on everything Miata related.
May be a a daft comment but just in case - the lid is lockable using the ignition key - just thought I would mention in case it was locked & the reason you couldn't find the lever!