Hi,
It sounds like you may have turned Takes to Layers on after the first recording, otherwise that first recording would have already been duplicated on an inactive layer. If you recorded fully over it while not duplicating the layer first, you can still get it from the Pool, drag it back into the track, and Move to Origin to get it back to it's time original position.
Going forward, if you're not sure audio that you are about to record over already exists on an inactive layer, use Duplicate Layer to get it there. Or maybe just leave Takes to Layers on all the time so it will always do that.