Ignore it. If you know you didn't do it, then its not your problem. They could potentially use your number as evidence, for example, they call your insurance company and say you hit their car. Suddenly they have pictures, your name/number (possibly to say you gave it to them after it occured), etc.

Not worth the risk.

I knew something was up. My chest hair has always been the same length. I had surgery a few months ago and had it nearly all shaved. It grew back so quickly and I thought to myself "if my hair grew back to normal length in a month, why isn't it 10" long in a year?". It seems certain hair must have a "terminal length" like you suggested.