how to fix my remote on 98 rav4?

i dropped my remote today at work and the battery fell out, noticed it said to replace within 10 mins or rolling code would change didn't get it done in time (couldn't find the battery) now can't use the remote to open the doors. called the AA the best they could do was to disconnect the alarm so I now have to use the key to open it and the lights flash for 30 seconds when you open it and when you turn off the engine. Really would like to get the alarm working again i've already had two cars stolen don't want a third.