Can you pull things out of a Bag of Holding if you don't know what's in it?

[Greywander]

I know you can just dump everything out. But lets say you get searched and for some reason they don't do that. As far as I'm aware, someone reaching into the bag can't just pull "something" out, they have to want to pull out a specific item that is in the bag. But how specific does this need to be? What if they reach in to pull out, say, a "weapon", would that pull out a random weapon, or would they need to think of a specific weapon? What if you're suspected of stealing an item, and it actually is in the bag, but they don't know for sure, so they try to pull that item out of the bag without knowing for sure it's in there. Would that work?

It could be pretty funny to have an NPC give the party a Bag of Holding, but warn them not to dump it out. The implication is that there's something already in the bag, and they don't want to let it out/know what it is. It could be something dangerous (like a monster that can survive inside the bag, e.g. a lich), something scandalous (like the corpse of someone important), or just something embarrassing (like erotic fan fiction). Should be fun either way.

[Mellack]

The bag has a volume that is not particularly large, just about a 4' cube. Why can't they just look in and see what is inside?

[Greywander]

I guess I assumed that that the extradimensional space that holds the items inside separates each item into its own private space. So if someone shoved you in a bag of holding, you'd basically be floating in an empty void until you escaped, and wouldn't be able to see or interact with anything else inside the bag. So looking in the bag you'd just see an empty void. But maybe that's not how the bag actually works...

[Witty Username]

Your more thinking of a handy haversack in that case.

[Mellack]

I guess I assumed that that the extradimensional space that holds the items inside separates each item into its own private space. So if someone shoved you in a bag of holding, you'd basically be floating in an empty void until you escaped, and wouldn't be able to see or interact with anything else inside the bag. So looking in the bag you'd just see an empty void. But maybe that's not how the bag actually works...

I thought it was just like a bag, except that it happens to be larger on the inside than on the outside. It even has a warning that the bag can be punctured.