I had a similar problem the end of the iPod that the wireless antenna connects to is indeed a ground of sorts it uses the case as the ground plate of the antenna. The frequencies of Wifi have a small wavelength and so its possible to fit into a small space. The little board thats stuck to the front/digitiser is the actual antenna. It is actually a PCB with one wire that snakes around itself you cant see it its in the middle of the board. There is one visible connection to the exterior connection. ie the little metal springy section that curves around the case exterior. Thats the ground plate connection. If you look carefully at the little board you will see what looks like a metal put attached to the board. That is a connector for an external Aerial you can get one of those if you have an old wifi laptop thats in pieces or something else that has had wifi. I have one from an old shuttle the connector is the same and you can fit the aerial onto the iPod boosting its range by about 80% I might add!!! The iPod aerial is poor beyond belief.
Anyway you can at least get hold of one of those aerials and use it for testing... Im not sure you would want to walk around with it connected tho ;) lol
Hope it helps