I doubt anyone has any 3090s in store.
Having no stock is also a complete possibility. It's hard to overstate just how fucked global shipping logistics are at the moment.
Some longshoreman somewhere could have 10 containers worth waiting for inspection and no-one would admit it publicly.
Even the lack of flight has fucked a lot of things, stuff like this where they sometimes fly stuff ahead of the boats could easily get capacity constrained and miss their window.