I would contact your real estate attorney. In most states there is a short redemptive period following the foreclosure auction. The timeframes differ from state to state. However, if you still have time to redeem your house, you'll have to come up with the entire amount owed on the property, including all fees, (usually the amount bid at the auction) in cash. Most investors won't invest that much money unless your LTV (Loan amount To market Value) is 60-75% or less. But it's an option.
If your house has been sold at foreclsoure auction to a 3rd party other than bank, you may be out of luck unless the investor who bought it wants to sell it back and then you need financing in place to be able to do so. if you just went through a foreclosure it is unlikely. your best bet should be to consult a real estate attorney. The time to save your home is before the auction, most banks will negotiate with you, just call and ask for the home retention department and there are several options they can go over with you.