All, having spent a lot of years at Drum I can tell you that Doghead is correct in that there are a lot of gravel parking lots and motor pool lots at Drum. Any while some have sand mixed in with the gravel there are certainly over a square mile of them.....
All of the items GL and GP have for sale remain government property. If I showed up and was told the unit I bid on, and have a receipt for by serial number, isn't available the first thing I'd do is to try to resolve the issue. Failing that and especially if I suspect something fishy I'm calling the post Military Police office and asking for someone to come to the site. Then, at the very least, I'd have someone disinterested to record the facts officially that an item of government property is missing and that they tried to substitute something else for the missing property.
I'd also call the MPs if I saw an employee tearing equipment up due to negligence or what amounts to vandalism.
On Fort Drum, like many other posts, the Military Police have jurisdiction over military personnel and not over civilians. It's the NY State Police that deal with civilians. An MP can detain a civilian but needs to call the NYSP to make any arrest. So, given that your dealing with a civilian employee of a contractor I'd maybe call the NYSP also and report an apparent theft as GL/GP says they lost government property.
And, if it were an off-post site such as a National Guard facility I'd still get someone to look at the serial numbers and confirm that they (GL or GP) had lost track of the item. All that may not help but it would sure get their attention.....
And I'm not sure if GL's disclaimer about serial numbers possibly being wrong in the sale listing matters when they've issued me a receipt with a specific serial number. That's GL making the statement of fact about that serial number and not a third party.
FWIW, I've only dealt with Samantha once and had a good transaction. But I've known at least three other GL employees at Drum to be thieves. 7-8 years ago, one offered to let me take things off some trucks that hadn't been lotted yet for a fee. Another time, one actually told me the day we met he would sell me things since he needed money for Christmas presents. On another occasion, there was a 20 ton floor jack that came up missing and when I asked yet another employee when it was going to be lotted he came right out and told me he sold it to someone who spotted it and wanted it. And several years back a friend showed up at my shop from picking a truck up with a bunch of boarding ladders and told me he'd paid $20 to be able to pull stuff out of the scrap bins. And another time.......
Lance