Have you taken it apart recently? I had to for my Tamagotchi Angel once because I accidentally dropped it in my glass of water, so I needed to air everything out.
h34r: Anyway, if you've ever taken apart a (vintage) Tamagotchi, at least, just make sure that everything is tightly in place. I had a row of missing pixels after putting it back together, and after tinkering around with it for a little bit and screwing everything tightly back together, problem solved! Another experience I've had with missing pixels was when one of the wires came off from the circuit board and so I had to soder it back on. Other than that, these are the only types of experiences I've had that MAY be similar to yours (I've never had the entire bottom row of icons missing). I hope this helps a bit, although each little problem is always unique. I would only do it if you're comfortable with opening up your Tamagotchi though.
