this is why you should always have extra caps in sealed bags, especially if you only bottle.
i keg everything, with a scattered amount of bottling with the beergun, but i got in on a deal for 3,000 bottle caps, so i am now good for the rest of my brewing career most likely. i put the caps in a 5 gallon plastic pale with lid with rice inside to help as a dessicant.
caps are cheap enough to have a lot extra. just remember to keep the extra all dry, otherwise all of your bottle caps will become rusty.