It never gets permanent
what medium? acrylic, watercolor? ink? did he explain why it would not dry?
I know a type of an oil paint that stays open forever until you heat-set it: http://www.genesisoilpaints.com/
is it this kind of paper - at Blick I found Yupo: https://www.dickblick.com/products/yupo-watercolor-paper/
OK, doing my research - it is Yupo paper (not Yupa), on his blog it is even a tag:
http://akirabeard.com/blog/keyword?k=yupo