If there was a viable business plan here, plenty of private investors would be lining up. The trouble is, there isn't.
I get the impression that you seem to think that Tesla asking the government for a loan means that they can't acquire funding in any other way.
It occurs to me that Tesla's issue is not money but rather the cost of that money. Certainly accepting money from private investors would require a loss of control/equity in the company. Or without the equity, having to repay far to much in interest.
The government loan option must appear to be pretty fantastic... Low interest rate loan and no loss of equity or control of the company.
If the government loan falls through and Tesla needs to raise more money, they will. I've no doubts that can get just about all the money they want, it's just the cost of doing so.
It's unfortunate they aren't publicly traded. I'd like to buy there stock... For a purely speculative gamble.