jfmgray - I've had to open a few cases with AP this year - they are usually quite slow, but I find that once you go onto their FB page and mention that you are waiting to hear on a case, you will usually get a response quite quickly. (Tip - don't write an angry FB message - always keep it upbeat)

Normally I tell my buyer that I have opened a case and that it can take a week or more to get resolved. I don't usually encourage them to open a case. Once AP get involved, the tracking information will update to say that there is a case underway.

Once AP have responded, (and assuming they can't find it), they will ask you what the items are and also ask you prove the value of the item/s that you sent.

I normally take a screenshot of the sale and send it to the rep who contacts me.

They will then send you a money order to the value of the items plus the postage and once the reps tells me that, I normally refund the buyer without waiting for the order to get to me as it can take a few weeks to process.