Cam a cam wear out?

Id put my money on the exhaust lobe on the cam is flat. This causes the cylinder to actually push the exhaust fumes out the intake valve since it has no where to go. Some other things to consider (if its chevy powered especially) are Broken exhaust rocker, Rocker stud pulled out of the head (which is really common on chevys witha big cam and press in rocker studs), Bent pushrod, faulty/stuck hydraulic lifter, or miss adjusted valve (lifter preload). Chevys are notorious for these different condition and I highly doubt that low oil will cause any of these conditions without a rod knock to go with it. You can find which cylinder it is by spraying water on the header near where the exhaust flange/head flange with the headers warming up after initial start up. You can also disconnect the plug wires one at a time and the popping will get less sharp when you find the cylinder. If the car is at the mechanic still then just pull the covers and take a look it will be obvious when turning the motor over with the starter. Good luck, if its cheap and has a lot of goodies it may be worth it.