As a fellow trader, I would echo that the customer has every right to get in touch with the vendor/manufacturer of their purchase and discuss their problem, be it missing or damaged parts. All manufacturers worth their salt try their best to make sure that the kit is complete and to as good a standard within their price range.
Any manufacturer who treasures their long built up reputation will be only too happy to make good defects as this engenders good feedback and helps the manufacturer keep an eye on the quality of their product for the future.
Yes, there are cheeky monkeys who want freebies, and others who completely mucked a project up and are after replacement parts bucksee, BUT, the majority of customers are honest folk who want to complete their project and cannot if there are faulty or missing parts.
So, do mention it in a topic and ask questions publicly, but make sure and get in contact with the vendor/manufacturer first to make good any issues. It helps you and it helps the hobby, and it helps the manufacturer to keep getting it right.
Be honest, we all lose things, we are all enthusiastic when we come to open that 'box of delights', and we are all on a learning curve, so mishaps happen as well. No manufacturer would begrudge you a bit of wire or to replace a poorly cast stanchion.