Yes. If the battery runs out, or you loose power to the opener for a period of time, you will have to reprogram the remote.
On the back of the opener motor you will find a 'learn button'. It may be under the plastic light cover, or in plain sight. It will either be green, orange, purple, or red. When you press the button an LED light just above the learn button will come on. Hold the remote near the opener and hold down the remote button. You should see the lights blink on and off a few times.
Try the remote. If this doesn't work try it again.
Good Luck!
Also, don't forget to check the balance of your garage door. This and other garage door maintenance tips can be found at
www.spokanegaragerepair.com/tips_tricks.htm