Battery died 2 days after being fully charged & load tested at O'Riely's Auto Parts Store

My battery was just fine a few days ago until I tried to start my 1990 Regal which did not have enough voltage to start the engine. I took the battery to O'Reilly Auto Parts to have the battery fully charged. After the battery was charged I then took the car to O'Reilly's to have the alternator checked. They said from the read-out that the alternator was not at a full meter when in idle, but it was fine when I pressed on the alternator. The 90 Buick Regal then started just fine and ran for 3 days, and on the 4th day when I tried to start the car in the morning the battery was dead.

I would like to know if the solution to my problem could be both the battery and the alternator. If not could there also be something else that would cause the battery to drain besides interior/exterior lights being on (which they are not). Thanks in advance for your expert knowledge!

Henri Mason
858 215-0559 It is fine to call my cell number if you would like :-)