My dad used to co-own a mid-sized general goods auction house that drew folks from all over the state, and got a few lucrative art deals that were floated upstate NY to get to the right bidders.
The question about stolen goods can happen, although how it's handled is dependent on how the merchandise was obtained in the first place and what the value was. (This information is related to U.S. entrepreneurial houses.)
They acquire their goods in 2 main ways: consignment and purchases. Consignment items are things that other sellers bring in, so everything from everyday folks with antique heirlooms to wholesale retailers who want to offload entire 'lots'. The profit from these items are split by percentage between the house and the seller, usually 30-70. Stolen consignment items are going to come out of the house's cut if the item was stolen before being sold, as the house failed to protect the merchandise. Items stolen after pick-up may be reported to the consignor, but they probably can't do anything about it. The major reason for this is that most items are unique. You can't really replace an antique heirloom. If you're talking specifically about high ticket items, like art or expensive jewelry, the house will immediately get law enforcement involved and check cameras, parking spaces/cameras, and interrogate employees. Theft heavily impacts how people look at that house going forward, so it's far from a casually accepted occurrence. Even the hectic, tiny ones will employ what are essentially bouncers.
Purchased goods, where the house goes out and pays a flat fee for entire lots or individual items (such as all the furniture and decorations from abandoned condos or 'temporary housing' that wealthy folks live in for a few months and then move on), also fall directly on the house if an object is stolen, however, they're not paying for the item and then paying an agreed upon amount with an outside seller, so the loss is in product rather than product+liquid assets in this situation. After pick-up theft is the recipient's problem, however, at least in my dad's case, after pick-up would require breaking into someone's car to steal an item. 9.9 times out of 10, goods were carried out by auction employees specifically to avoid that kind of shenanigans, and small items like jewelry were handed directly to the bidder after winning. People would sometimes leave, drop their things off at home, and then come back if they had larger items that were easier to take out of a car or back of a truck.
What I really wanted to emphasize for your writing pursuits is that any house bringing in customers is going to have some kind of law enforcement or private security on hand during auctions, even the little hometown ones. The mid-sized one my dad co-owned had a weekly Thursday night auction, and a special weekend auction if they had an abundance of quick-selling stock. Every auction night, the local police force assigned 2 dedicated officers: 1 patrolled the grounds and 1 watched over the auction for the whole 4 hour event due to the amount of traffic it brought in. Really high ticket items are going to have private security on hand. Those paintings that got sent to NY sold for half a million a piece, I heard, and I believe them because the owner of the house that my dad's AH consigned with drove halfway across the country to pick the paintings up and
personally escort them back to NY. These aren't open flea market type-events. Security is a must (it sounded like you were talking about really high priced items), so there's a real life example of what the house will go through to ensure security is tight. The employees would be another obstacle for thieves to consider. The auctioneer may be facing the crowd and rattling off a number rhythm, but the people working behind him to showcase the merchandise and anyone working outside, the folks loading up cars with purchased goods, as well as the people working the window who accepts payments and issues paddles/sticker/whatever bidding method the house uses, also keep a wary eye. Not even kidding, the other co-owner had a parrot who lived in the auction house that would screech when people walked by him -- his placement near the back door was not accidental, though he was a cute distraction for the kids.
Picture many employees, private security and/or actual law enforcement, a consignor who wants to guard their stock, and any regulars that like to pretend they're employees too (happened all the time) all watching like a hawk. In the eight or nine years that I knew my dad while he co-owned that place, I can count on one hand how many times something was stolen and the thieves actually got away with it. It was more likely for fights to break out and the officers to get involved than anyone to get away with theft. An item stolen after pick-up would need to be small, or extremely well planned and likely require multiple people to pull off.
I hope some of that helps!
