Should I be concerned with being fired and what should I do?

I pulled my boss aside the other day at work. I asked her why i haven't been on a register at work. She responded with "I was waiting for you to ask. The district manager believes someone is stealing from the store. She told me to pull off the top 3 cashiers and see if i can isolate which one is stealing." She went on to say, "I don't think it is you i think it is the other girl which we are pulling her off next week." She said they are pulling the cashiers off one by one for a week at a tiime to see if they can isolate and see who it is doing it. I did not, am not, and never would steal from my job. the problem is, the day I was pulled of the register was the same day the suspected manager quit. I'm afraid that if the issue clears up while i am off the register that they will think it is me and it could be the manager that quit who was doing it. The same day she told me that she gave me her password that works everything in the store. And she gave me more hours for next week. Should I be worried or not. She said that if they don't find out who is doing it that everyone will be fired and they will have to hire all new employees.