Mystery Drain on Battery

I have a 2001 Esteem GLX wagon with 135,000 miles on it. 6 weeks ago I had a new battery and alternator installed and all was fine until Sunday when I unloaded some dirt from the hatchback. Apparently, when I shut the hatch, the rear dome light came on. The next morning, the car was dead as a doornail - electric locks wouldn't work, couldn't shift, etc. Started right up when I got a jump, let it idle for over a half hour and then drove 6 miles to work. When I came out 4 hours later, it was dead again. Charged over night on a trickle charger, but it was dead again the next morning. Took it back to Pep Boys and they say the battery and alternator are fine, but there is a 5 amp drain when the car is turned off. They pulled all the fuses and couldn't find anything, so they recommend I take it in to the dealer. Anyone have any ideas - I hate to keep dumping $ into it and I've had electrical problems with other cars that were never resolved. Thanks!

Is your rear dome light still staying on? That is enough of a load to drain your battery over night.