Trusting friends

I wouldn't mention it. It's just a mug. Doubt if the charge was very much although thats not really the issue. I would be miffed at being charged for it though

What would people do if it came to light that she had or almost certainly had taken the mug?

I'd ask her in person, not on the phone, so I could see her reaction.

These sorts of situations make me squirm with embarrassment for the other person.
They make me so uncomfortable.

Next time you have coffee at your friend's, you might spot it! After she admired the mug it seems too much of a coincidence that one goes missing. She needs to know you've been charged and reimburse you.

Yes of course I'd mention it, as MissAdventure says give her the opportunity to "fess up" then she can pay for it lol

If she's a good friend I would definitely mention it. What a mean spirited hotel to charge for a mug!!

I'd throw her a lifeline by saying "I don't even remember breaking it, do you?", so she has a chance to save face and perhaps remember breaking it herself.

I think I'd mention it. Mumofmadboys's suggestion of mentioning it over the phone sounds good and I'd do that in your position.

I would casually mention that the hotel charged you for a mug they claim'we have lost' and see if anything is forthcoming. Could you mention it over the phone- may be easier.

Yes I'd mention it even if it's to ask if it was broken, as a reason for the charge. Act daft.