A property that I have title to was forclosed upon and sold by the bank last week without my knowledge. What can I do?

You have not provided enough information for a definite answer.  You say you held title and that the property "closed" on 5/20.  These two statements imply that when you purchased the property you gave a note and deed of trust, you defaulted on the note and there was a trustee's sale on 5/20.  If that was the scenario and you did not receive notice of the default and upcoming sale, then the trustee sale should be invalid.  However, it would be extremely rare for a trustee to make that mistake.  Therefore, I suspect you had an installment contract because you say you were making payments through escrow.  On an installment contract, title is not transferred to you until you finish paying all the installments.  Unless a "memorandum" of the installment agreement was recorded, no one (i.e., the public) is aware that you have an ownership interest in the property.  To "foreclose" on an installment contract requires a lawsuit/judgment, rather than a trustee sale (i.e., closing).  Since it would be impossible for you not to be aware of a lawsuit against you, it does not sound like the installment contract was foreclosed.  Instead, it sounds like you purchased the property "subject to" a mortgage/deed of trust the seller was supposed to keep current (using your installment payments) and the seller failed to do that, so his mortgage/deed of trust was foreclosed and resulted in a trustee sale.  That could happen without you getting notice, in which case you'd have a right to sue your seller for breach of contract but would not have a right to get the property back from whoever purchased it at the "closing."  You need an attorney to review your paperwork and more facts about your case.