I was attacked when I was asleep recently and lose. I lost over 10000 soldiers but when i got online..

For the attack, check the battle report to see what happened. If your hospitals are full then soldiers will not be wounded they will die. Also there are research / premium perks that will cause defeated troops to die instead of being wounded, your attacker may have had these.

The shield may have been timing. There was a server update recently an when this completes all bases are given a shield for around 30 minutes.

There is a special feature in the game the first time you have a major attack that applies a 24hr shield and heals all wounded. This only applies to the first time.