The 1.21 BC was in a single "chunk". When you sent 0.01, you made a transaction with one "in" (the "chunk") and two "outs": one sent 0.01 to whoever you sent that to, and the other one sent 1.20 back to you as "change". This second "out" was sent to a brand new address that you just generated. Since your old wallet.dat doesn't have the keys to this new address, you don't see it.