Possible Clues:

• Digital in the extreme!
• Tot getting hint in part of index, perhaps
• One type of police search means the end for Pinkie, perhaps
• "If you keep sucking your thumb, you'll gross out your friends"?
• It's printed?
• Altered print, eg if manipulated digitally
• Such delicate control: grip net if loose
• Touch on clue one's nailed!
• Identification means
• Digital appendage making print if eg misshapen