Why the Premishlaner Rebbe Really Did Give Bad Advice

A few days ago I posted that the Premishlaner rebbe said that the stock market will take a nose dive on Wednesday. This has obviously not happened. However I suddenly had a thought - the original Rotter post claimed that the  Premishlaner rebbe told a prominent banker that he should quickly sell all his stocks because the market was going to crash. However it occurred to me he should of just advised him to go short on the stocks - in todays world knowing the stock market is going to go down is an opportunity to make serious money. In a response to a comment on the original post, I suggested that it is a well known rule that negative prophecy does not have to come true - since in the interim the person might have performed teshuvah. However I now think that any knowledge of the future of the stock market is intrinsically a good prophecy - you can make your money either way - and hence it really should have happened!