Because no-one is available to lend it to you..... probably because they all think it will fall, or are not willing to take the risk. You need two sides to make a transaction.....
How can I see what my effective investment is in an equity or index? The closest I can get is to select 'close' and see what the return would be - butsincve we know the profit/loss and initial investment amount, it should be easy to see.....