key Problem 2002 525i

I had a colleague get something out of the trunk of my car and now the remote does not work......I tried to reprogram/initialize the key, but no such luck...I followed my bentley manual by holding in the memory 2 button and then depressing the memory 1 button (3) times and then starting the car.....I also tried a thread from someone on Bimmer Forums that had me opening the trunk first then getting in the car and going through moving the key till just before starting (5) times and on the 6th attempt start it.....No Luck.....Is it possible my battery in my key is shot???