30 missing is a lot but is it really 30? Half inch end mills disappear like candy around a machine shop, guys grab one for a quick job and "forget" to sign it out, or it breaks and nobody wants to write up a broken tool ticket. I'd do a real count twice before I start pointing fingers at anybody. Check the scrap bin and the bottom of the coolant tank first, that's where half my "stolen" tools usually turn up.