[Random items disappearing from inventory]

I know 100% that I bought a full set of loki prime from someone for 300 platinum, and I've gone to sell him to someone else later down the line and my systems have vanished from my inventory. Like completely gone, I've effectively lost 300 platinum for no reason, the blueprint isn't in my foundry or inventory, I've not built it, and I know for a fact I bought the full set. Can i either get my loki system back or recieve a new one or something because otherwise I've just lost all my platinum, the same thing seems to have happened to someone I was buying from earlier who was sure he had odonata prime wings but they weren't in his inventory when he went to sell them to me or in his foundry, so random prime items are disappearing from at least 2 players foundries and inventories, completely bankrupting me.