I can't imagine a service that would have a policy other than "Hand them the damn narc box." for a couple of reasons:
1) by and large, narcs are cheap. Even buying in low volume, the typical narc box has well under 50 dollars worth of meds in it. (Side note, I could see having a hand gun strapped to the back of the lifepak.)
2) Losing narcs isn't as big a deal as people think it is. If you have a legitimate reason for losing them like, say, "A guy pulled a gun/knife on me.". The process boils down to conducting an internal investigation ("So, a guy pulled a gun on you guys, huh? That sucks."), filing a report with the local LEOs (Which you'd probably be doing anyhow.), and doing some paperwork to notify the DEA.