How to reproduce: go to biters' hatchery, place factory fast, and get in. The biters start to attack this your factory, just wait and sit in. If biters destroy your factory, you are still there. You can collect everything inside and get out with all this loot. Also, you can wait before biters go away. I think it's bug.

The proposed scenario: get you out instantly if your factory was destroyed. All items inside should be deleted (I mean you can't wait, collect something and get out with loot)

1) The loss of a single factory building is often enough to make players just reload an autosave instead of continuing without it. 2) There's seldom a situation where you place factory buildings dangerously close to biter territory anyway. 3) There's a cheat command to respawn your 'destroyed' factory buildings, which would lose much of its functionality if the interior of a factory building was truly destroyed instead of just being trapped in limbo.

I guess I could still teleport players out if their factory buildings were destroyed, but I don't think that's important. Pretend it's a feature.

maybe teleport it out, and lock the factory to enter in?
I will check your code on github later - too busy now :)
And then maybe I will provide a good pull request for this issue

I have several suggestions for improving the external presentation of factories, as well as the behavior and operations with factories. But I need to first look at your code and API capabilities - will we be able to do this at all?
Anyway, I'll try to hit you later.