I would never let anyone borrow my guitar. If both pickups don't work, I would first check to see if the jack is properly working. Sometimes the guitar cord plug can bend the jack internally or the jack can twist and short out. Look inside to see if they decided to rewire it or change other broken components. I would suggest before lending your guitar to someone make a schematic drawing of the circuit. This helps if you're doing a modification and makes it easier to remember where the wires go when you side-tracked after a phone conversation or talking to a customer. Take an Ohm meter and check the entire circuit. If there is a complete short in the circuit, then you need to thoroughly check all wires or have a repair shop evaluate what the problem is.
Very seldom do pickups go bad unless someone decided to mess with them and perhaps pull the covers off and do some experimental modifications. If the coils are broken you will need to seek a qualified repairman and give your friend the bill. Make sure you have the original pickups in the instrument and didn't get switched because somebody liked yours better.
WRITTEN ON JUNE 12, 2015, BY