JNX0Z7SP is an interesting fare ... was filed in October last year! Fully refundable too. June onwards there is good mid-week availability.
But it doesn't price for me anywhere. Our corporate system tells me 'no fare available'. Hmmm, tempting. In which SQ fare class does this map?
WebJet indeed seems to price it ... on JetBlue directly is shows: Flight is Sold Out or does not operate (N/A) on either of these dates.