Hi, I hope someone can help me figure out what may be wrong so I don't have to spend too much money at the garage!

Car is a 2001 Civic Si

Everything was working fine until a month ago I came out of the store and the car wouldn't start. When I turned the key there was no noise at all, it was completely dead.
The guy at a garage came and gave me a boost and I was able to drive across the street to the garage (very convenient place to break down!)
So they hooked the car up and tried to test the battery and the alternator. They determined the battery was dead, but couldn't keep the car running long enough to test the alternator. They went ahead and replaced the battery and were then able to test the alternator and the new battery and the alternator both passed the test.
The next day I noticed the the following things don't work anymore:
*no radio and no clock (nothing on the display - the book said I should see Code to reset the radio - but there is nothing)
*the power locks only work when the car is on
*the interior lights don't come on when the door is opened, but they do work if I turn them on manually.
*if the headlights are left on, the beeping doesn't go off when the door is opened.

Everything else works - power windows, moonroof, headlights, mirrors.

The fuses have been checked and nothing looks wrong with them...and I'd suspect if it was the fuse for the locks that it wouldn't work at all - not just when the car is on??? Very strange!

I don't know much about cars at all, but I'm wondering if this would all be connected to the new battery? Maybe it wasn't connected properly?
Note: the battery that was dead was original to the car.

 

It was the fuse labelled Interior lights....but the interior light did work when I manually turned it on? So, I have no idea why that would be.
All fixed, radio code entered and I'm back in business.

 

I had no idea. Very interesting. So that fuse was actually blown even though you checked them good???

 

I can't guarantee 100% that my dad and I checked that one. I was pretty sure that we checked all the ones under the hood, but may not have checked that one since the interior lights turned on when I flipped their switch manually.
Lesson learned - cars don't make sense and check all fuses no matter what the label says.