@ElliotBrown0944 The seller supplied a collection booking, while the agent's warehouse reference shows no arrival. Although our packing list includes the arm and the tool connection cable, neither message identifies a received crate against that order.

Send both references and your crate identifier to each party privately. Ask them to link the numbers and say who last physically received that crate.

Would it help to put both parties on a single message? Passing their unclear answers between separate conversations is getting frustrating.

@TheoAdams0149 I used a shared conversation on a separate freight purchase. Once the contacts could see each other's references, I no longer had to relay and interpret their replies.

Yes, use your established contacts. Once they map the references, the location should be clear.

I now have the agent's confirmation that it received our crate, with the seller's reference linked to it. The disputed handover is accounted for, though delivery is still outstanding.

That accounts for the handover. The outstanding delivery is a separate question now.