Battery Dead problems of the 2004 Mercury Mountaineer

After not driving my vehicle for 2 days the battery level is low, the red indicator lamp on battery is showing, and my vehicle will not turn over. I connect my jump-it and it starts right up. I have taken it in to midland Ford several times and they tell me that they cannot find anything wrong with my vehicle and they cannot replace any parts unless they can find a problem. They want me to leave my vehicle there for at least two days to try to replicate the problem, but refuse to provide a replacement vehicle or rental car or I have the option to have my vehicle towed in to midland Ford at my expense so they can verify that the battery is actually low in order to replace it. My 2004 Mountaineer only has only 21000 miles on it and the problem started occurring around 200 miles and is getting worse as time passes. Last weekend after driving home from work I decided to vacuum out my vehicle using electrical from my house for about a 1/2 hour and I did not even play the radio or have the ignition key turned on. When I was finished, I closed up the doors and did not enter the vehicle until the next morning when I was leaving for work and again the battery was dead with the red light on. I took it in again and midland Ford said they could not find anything wrong and they cannot replace the battery. I feel very confident that if the warranty were to expire they would not have an issue with replacing the defective battery at my expense.