Someone can not ask or demand the tenants to leave with little notice, they have to be given, BY LAW, a 60 day notice to vacate.
You can verify whether the property has had the Trustee's Sale by contacting the customer service dept. of a local title company or you can contact the County Recorder's office. The notices are also posted in a local newspaper...so you may want to check online.
However, even if the Trustee's Sale has occurred you will not have to leave with very little notice. If you have signed a lease or rental agreement it is valid with the lender and they will make arrangements with you as to moving out. Typically they will send you a letter or post the property. Then they will send a representative or real estate agent (whom they will list the house with) to discuss the situation.
If nothing can be resolved after those contacts, then they could start proceeding for eviction. But most lenders want to work things out with the tenants and at times will offier incentives such as cash for keys, so that the property is left in a marketable condition. Due to the backlog in California, my experience has been that most lenders take several months (ie. 3+) from the start of the foreclosure process to obtaining possession.
All lenders are different and can do different things. But based on my experience this is typically what happens.
However, I am not an attorney, and you may want to consult and attorney for legal advice.
Mike Broker Assoc.