I haven't had anything completely disappear, but there's a bug when buying / selling from / to carriers, then your cargo appears as empty or full. For example if you buy from carrier, cargo wont appear in your inventory until you re-visit market. First time i saw this, I panicked and was like "WHAT THE F, WHERE IS MY CARGO?" but it re-appears as soon as you visit any market. Maybe similar thing exists with carrier?
If it never re-appeared, then no idea.
I did once notice that someone forgot sell order on Agronomic treatment, I bought everything for like 3 mil and sold for 250 mil lol. I looked it up on Inara and that carrier showed up, so I went to buy it all.
Sell orders don't always have to be put in, I almost made same mistake on my carrier. When I dropped some off into my carrier via "transfer", then somehow it was up for sale for galactic average, no idea why / how. So now I always check my carrier market TWICE when I add any new items.