I feel this has been exhaustively explained and reexplained throughout the thread, so the answer is: maybe...if the shop owner knew or should have known those items would be used in the commission of a crime, then yes there is potential liability. In your example even if the kidnapper didn’t disclose his intent the particular grouping of items may in fact suggest the shop owner knew or should have known, and of course other facts are relevant. For example, it’s a small town and the shop owner knows the purchaser as a felon with a history of violent crimes using duct tape and a ski mask.
That said maybe the facts suggest the shop owner didn’t know and had no reason to even predict the items would be used in a crime (maybe these are items typically purchased together from the shop).
As dragonwriter stated these cases are typically negligence cases, especially in firearms/ammo cases where there is federal law to protect arms dealers (thank NRA).
Here is a link to an article about a ammo case against Walmart (sold bullets to a drunk guy who gave the bullets to a kid after walking outside and 15 minutes after purchase shot and killed someone), my guess is Walmart won’t be found negligent. The article notes a second case where a gun shop sold a gun to someone who workers had suspicions was buying the gun for someone else (the gun was bought for someone else who used it to kill 2 police), they were found liable. https://www.google.com/amp/s/www.cnbc.com/amp/2016/01/08/wal...
Here is a second article against Walmart again where Walmart entered into a confidential settlement before trial. https://www.google.com/amp/s/www.mcall.com/news/breaking/mc-...
Sorry don’t have the time now to pull up the case styles.