Crew's gang box got hit over the weekend - does anyone actually recover tool theft costs?

Your GC is half right, unfortunately. Builder's risk policies almost never cover contractor or subcontractor tools. Those policies are written to protect the structure and the building materials that are part of the work, not personal property belonging to the trades. Some policies have an optional endorsement for tools and equipment, but you'd have to ask to see the actual policy to know if his has one, and even then it usually caps out low. The realistic answer is each sub's own inland marine or contractor's equipment policy is the route, and yeah, the deductibles on those are often brutal for a small claim. One guy on my crew learned the hard way that filing a claim under his deductible just gets his rates jacked anyway. Worth a polite ask though. Get it in writing that the GC says it's not covered, because sometimes the answer changes when someone has to actually put it in an email instead of shrugging at you in person. I've seen a GC magically find coverage once a sub asked him to confirm his position in writing. Either way you're not picking a fight over a few hundred bucks a head, you're just asking a question. On the cops, one thing that helped us was calling the county sheriff directly instead of waiting on the city PD follow-up. Deputies around here actually checked the pawn shops and online marketplace listings in the area, and a buddy got a couple impacts back that way. Stolen tools with serial numbers and scribed marks turn up more than cops let on, but only if somebody's looking. File your own reports even if the GC filed one too.

As for hauling gear, I stopped leaving anything on site years ago and I get ribbed for it constantly. Then sites like yours get hit and suddenly everyone's asking how I load my truck so fast every night. A job box with a real lock and a hasp that's welded or recessed helps against the casual grab, but if somebody brings bolt cutters onto a fenced lot, nothing portable is stopping them. Cameras help catch the guy, not keep your stuff. Six weeks left is a long window, so if the subs can stomach the daily load in and out, that's honestly the cheapest insurance there is.

One thing that worked for us on a long build a while back, once we got the roof and doors on, the GC let us lock our stuff in a back room of the actual house instead of the site box. Way harder to break into quietly than cutting a lock off a chest out in the open. Cost him nothing, kept the peace. Might be worth asking yours since you've got six weeks left. Also I paint pen my initials under every tool handle now. Cheap, takes ten minutes, and I know what's mine if anything ever turns up at a flea market.

Back in the 80s we used to chain the gang box to a concrete block buried in the ground. Took two guys and a truck to steal that setup, and nobody ever tried. Cheaper than one of those fancy containers too. These days I just do what my old foreman drilled into us: tools ride home every night, no exceptions. Lost maybe twenty minutes a day to loading and unloading, but in forty years of construction I've had gear stolen exactly once, and that was off an open trailer, not a box. Also, engrave your phone number on everything, not just initials. Cops can actually match stuff back to you that way if it turns up at a flea market or a yard sale.