Further update
My credit has still not posted, and as I suspected, it's because the charges were in two separate postings, one for the prepaid deposit (specifically allowed as a qualifying purchase) and the other the on-site hotel spend. The AMEX agent I spoke to said that the terms should have stated that it all had to be one charge to qualify, but they acknowledge that the terms did not say that, so the credit will need to be handled manually, which they will do. It does, however, seem that you have to contact them to get action.