Actually yeah.. didn't know that it only worked outside of GZs.
Yeah, it's kind of confusing. Sometimes when you steal an item in a GZ, and you are guard whacked, depending on whether or not you ran far enough out of the GZ, you can actually end up keeping the item. So never try to hide inside of a GZ after stealing an item, run as far out of it as you can immediately to hide. If you steal an item in a GZ (even if you steal an item outside of a GZ, then run INTO a GZ, this will happen), without getting guard whacked, and you run off and hide, but are found and killed while criminal in the GZ, the item will return to the victim. However, if you steal an item in a GZ, without getting guard whacked, and manage to run off and hide in the GZ until you uncrim, but you are found after and killed, then the item will drop to your corpse (unless insured). That's why it's always a lose-lose situation to hide in a GZ after stealing an item. Man, looking at this paragraph all i see is GZGZGZGZGZGZ lol.
But if it's an unnoticed steal at a bank, you can bank the item immediately. If it's noticed, you can't bank it until you lose your criminal status.
Also, NEVER insure an item in a GZ right after stealing it and going criminal. A guild member of mine found that out the hard way lol. He found a dude afk at the Fel Yew gate, with some nice armor in his pack. No one else was around. So he would steal a piece of armor, insure it, then steal another. On like the third piece of armor, someone showed up at the gate and called guards, and he got whacked. When he rezzed, he checked his pack...nothing there. He goes and snoops the dude. All the items he had just stolen within the previous 2 minutes (or however long criminal status lasts, it's 2 or 3), were inside the guy's backpack again, INSURED. Basically, he took the guy's items, insured them for him, and "returned" them.
So yeah, wait until you are officially outside of a GZ to insure anything recently stolen lol.