Lucky 13 was probably all two guys could carry, what with bolt cutters and stuff. As said, if they had known it was 50, they would have planned to take them all.
As for stealing gov't guns, it's why police cruisers are now monitored in some way. Just like not leaving your HMMV abandoned on the streets of Baghdad when searching a building, the cops now have to secure the vehicles contents in careful ways because Uncle Sam has been handing out full auto M16's to departments nationwide. The cruiser was already a target if left alone, just from vandalism, leave it where a perp can see guns inside, they are after them in a heartbeat. Now, every one potentially has a full auto M16 in the trunk. No way the cops can leave them unattended for long periods of time.
Cruisers are getting broken into at an increasing rate. So a couple of freight thieves hitting a shipment of AR15's is just chance. No way you could know in advance which CONEX of 150 on a train would have that box and where it was loaded in the car. It could have been behind 25 refrigerators.
S&W and the shipping companies do play a game were the shipper isn't listed right out in the documents. Those of us who returned our LCP's by recall didn't see "Sturm, Ruger, and Company, Gunmakers to America" on the label. IIRC it was "SRC" and that's all it said. Got it back to my doorstep the same way.
Which should explain why the load wasn't behind all those fridges - the anonymity of shipping that way is the protection, key an indicator on the label to create more work for the loading crew and you just told them what's in the crate. It's the same way jewelry is shipped - nobody labels it "South African Blood Diamond Mining Company" to "DeBeers, Amsterdam."
Not even the military sends guards on train loads of vehicles and equipment shipped cross country. What you do is not leave anything obviously labeled or unsecure, the train shipper attempts to park it in places far removed from public access to prevent theft and vandalism. It seems to work out overall. Commercial? There's no way to house a guard unless you add a car built specifically for it. Sitting three days in North Dakota in subfreezing temps miles from town in a blizzard isn't going to recruit many job seekers. Not happening, and exponentially escalates the costs.
The unintended consequence is that gun prices would easily triple . . . sounds like a great scheme if it was proposed by the anti gunners. And it would do very little in theft prevention, most stolen guns come from homes, or BATF operations.
Note there's NO reward for all the guns they let walk during Fast and Furious, they even know the exact serial numbers. They were monitoring the operatives and had to know which one surfaced where. Like the ones used to kill other Federal agents.
No doubt they have the SN's on the missing S&W's, you guys there need to keep that in mind.