Israel invades the gaza strip.

Uh.

http://en.wikipedia.org/wiki/Killings_an...estine_War

Yes, I'm very well aware of the fact it has both sides casualties on it.

Actually, it doesn't even matter, for the sake of this discussion, what actually happened.
None of them could see the future. It's only logical to prefer to save your life than your property.
However, it's equally logical to realize that anything left behind would be seized by the enemy. Expecting your enemies to be murderers but not thieves is a bit absurd, don't you think?
They were "expecting to return" because they were expecting the Jews to eventually be defeated. That hasn't happened yet.