I have seen trustee sales rescinded more than one year later. The Civil Code does not set forth a time limit for this sort of thing.
If you were a "bona fide" purchaser of the property, you may have legal rights that would prevent them from not releasing the trustee's deed upon sale to you. You should seek advice from a qualified real estate attorney in your area.
Nothing in this response should be construed as legal advice, or establishing an attorney-client relationship.