The Missing Finger

I just noticed that Duane’s finger is missing. 
You met Duane recently, he’s the guy I’m teaching to drive. 
“Duane! What happened to your finger?”
When he was a tiny baby, he was left alone in his crib drinking a bottle of milk. 
A rat crawled up into his crib and started chewing off his milk covered finger.
 His mom came home and found him two hours later.