Accused of Theft; Police Found Nothing?

I was accused of stealing a customer’s ipod touch that she claims she left on the counter. In the span of a minute or two, she left and came back in. I didn’t take it. Other customers were in the store. Two left, a third and fourth said they saw no-one else come by the counter and the father of the customer – who was outside in a car – said he saw no one else near counter in the short time daughter exited and re-entered the store.
The police came, interviewed everyone and searched me and the area -coming up with nothing. Everyone left and I wasn’t charged with anything.
Is this over? I was never charged and the last thing the office said was “if it turns up, give me a call”.
I am worried that if I have to take a lie detector test, I’ll fail (since they aren’t 100% accurate) and be charged with this theft which I am not involved. The evidence is circumstantial against me, and there is no way of knowing (in my opinion) with 100% certainty that one one of the other four people did NOT take it, somehow.