Lost every Silverado key?
With no Silverado key left, we mill the blade from the VIN's key code, and the work happens where the truck is parked. On many 2007 to 2013 trucks, GM's relearn then runs three rounds of about ten minutes each, key in the ignition and the security light on, so count on half an hour of waiting.
Later trucks program through the OBD port, where some add a GM security timer.
Lost-key work puts $60 on the key price, so a 2012 truck comes to $125 plus $60 and a push-start 2021 to $229 plus $60. Proof of ownership means the truck's registration or title plus the owner's driver's license. Chip-key trucks get the missing key wiped free of charge after the new one starts. A chipless 1999 to 2006 Silverado just needs a fresh key cut to code.