Hello Enzo. Your rate is only locked in if asked your lender to lock in your rate. If your rate was not locked in, then it will continue to fluctuate with the market.
Rate lock agreements are generally only valid for 30 days, but may be extended for longer periods of time by paying a fee to the lender. As Cynthia points out, it will be difficult to lock in your interest rate when you are purchasing a short sale because most short sales do not close within 30 days. Thus, even if you lock in your interest rate, if you do not close escrow on the property within 30 days, the interest rate will re-adjust to whatever the lender's rates are at that later date.
I hope this helps! If I can be of further assistance, please let me know. - Sat Aug 23 2008, 11:08