In this particular case then, the client and server had an async error, and the server stopped the meseta being banked, although it would have disappeared from the inventory client side. Relogging to refresh the character state (to match what the server has) would fix it.
Before making threads like this, always change ship to refresh your character. This wouldn't mean if the items are still gone, we'll restore it, but we'll possibly be able to see why it disappeared.