Were you on a *A flight, likely TG? If so, you should earn miles assuming it is a mileage earning fare class.

For bmi you earn 50% on TG in W: https://www.flybmi.com/bmi/src/html/...earnmiles.html

For UA you earn 100% on TG in W for domestic flights: http://www.united.com/page/article/0,,1194,00.html

SQ doesn't seem to publish this information, but I would expect some amount of miles for that flight.