Mesoamerican gold was looted and melted down wholesale (along with a lot more silver) by the Spanish. The artefacts were considered unchristian and so were deliberately destroyed, and this has meant that we have barely a fragment of the artistry of the Inca and Aztec.

There is some hope though! It's thought that the melting process was done in Spain so as to allow a reliable royal assay, if so then some of the ships that sank in the trade may have holds full of crushed and squashed precious artefacts.