an interesting record.
David Mohn has found this caterpillar on a fern in 2007 while sswroom has pictured the same in Tai Po Kau in 2007 and 2009.
It is likely a Noctuidae moth - Callopistria sp. and could be C. juventina (Stoll, 1782) Sugi in Inoue et al., 1982. But the correct ID is uncertain. If the caterpillar is still on your potted plant, try to rear it to adult to see what species emerges eventually.