I was wondering when and how often do tanki release new hulls and turrets?

What do I do if I lost containers? I lost 6 of them caught from the last event (hopping railgun golds which I caught 12 or something) when opening them and then there was a bug and I joined a battle even though I didn't press it and then I was about to open my containers and then? I lost my rewards. Please help me get them back and tell me how.