Best thing to do is check your purchase contract, haven't seen one for Oasis but they are all based around a standard contract! I would say that you have most certainly lost your deposit, I would imagine that if the apartments were selling like hot cakes then HDA would have been in a better position to work out some sort of deal, but as we know they are not, so little chance under current circumstances to get anything back!
I was surprised to read that your lawyer thought that HDA could try and make you complete, again there should be a clause in your contract covering the circumstances of none completion! Sorry for you, Oasis is really starting to take shape!