92 Lumina car battery drained not sure why.

What is your question?

I just went out to my car to find out the battery was dead. The lights were not left on or anything I double checked immediately. Recently with the humidity and heat my rear view mirror became detached, I needed to go so I removed the electrical wire to it, so it was not dangling on my way out. My question is could it being detached drain the battery? Otherwise I have no clue what could have done it. Thanks in advance!