As long as you are not a shareholder, legal representative or senior manager, there is no problem. Gold is a currency and a strictly restricted commodity, whether in China or other countries. As long as the procuratorate decides not to prosecute him, it will not leave a criminal record. The longest detention 14 days is stipulated by the criminal law. If you are prosecuted, because the case involved is not deep, and non-violent crimes are more likely to be released on bail pending trial, that is, you will pay the deposit and release the person, and the judicial department will arrive at the case in time when required.
If the worst happens, please call a lawyer in time. But according to what you said, there should be no problem. (It is possible that the prosecution will ask to be a tainted witness.)