I'm not sure about this. Since they are doing that deal to avoid the taxes of the buying operation, I think some risk should be added to that. Therefore this wouldn't be considered as scam.
However, I'll let an admin give a definite answer here, cause I'm not sure.
It's a scam.
Even if you had knowledge IC or OOC of the deal, they were personally handing over keys to each other after taking the money. There is no possible explanation for you to run in between and get ownership.
This is mostlikely powergame in my opinion, its impossible to do that IRL. However I think its not a rulebreak. If you look at this as the material warehouse. People can just run And steal the whole materials there with one simple command.