For further information you have to check with your local Post Office. I suppose, this could be done on-line - this further information is in Japanese and I can't help you within your homeland.
I hoped the matter will dissolve on Monday with a happy-ending, i.e. safe arrival of the parcel.
Nevertheless, I am here to smooth the transactions for the artists and the buyers equally. Whatever the outcome, it will be dealt accordingly.
Please tell me what the local post office is saying.