Tuta: There are many banks and many loans. The best thing to do is to shop around. Not all lenders work in the same way. You may find one who will accommodate your deal, FHA or conventional.
On the other hand, we don't have a clue as to what the bank did not like. It could be that the appraisal came in low. If that's the case, a bit of negotiation with the seller may be in order. He may have to lower his price to get the property sold.
Finally, the sales contract could now be voidable. If you do not have a mortgage commitment, either party can usually call it quits. If the seller has other prospects, he or she may well want to move on. You might also wish to do the same. Either of you should be able to cancel, if the contract is written that way and most of them are.
Lots of Luck.