@Erika741 Guests often don't respond to messages, and it may be that they just don't have their notifications turned on so don't even realize there's a message waiting.
If a guest doesn't reply after a few days, you can try sending them a text message to their phone number.
For a missing item, the guest may not reply if they feel they are being accused. I have no idea how you asked them about it, but something like " Hi XX, thanks so much for leaving the house so clean, we really appreciate it. A question, though- the medium size saucepan seems to be missing- just wondering if you put it somewhere we didn't think to look, or accidentally packed it with your stuff? No biggy, it wasn't expensive, it's just a bit of a mystery", shouldn't lead to them feeling defensive.