Wondering what you use to see if supply line has been tampered with after our install

Curious what you use to verify if a supply line has been tampered with after our installing it. We have a customer that had a toilet supply line crack at the tank side of line, it is a toilet that we installed 2yrs ago but it is not a brand or type of supply line that we have ever used. We currently put with sharpie pen the date on the line. But know Im thinking we need to do more than that to be sure that it hasn't been changed out or disconnected for that matter for new flooring or painting. Makes ya think when you know u didn't do wrong.

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