I think they have a complete tracking system for all space debris and as you mentioned the onboard radar should have avoided such as well. Plus, I think the crew would have reported something like that (it's not like they wouldn't have felt it I don't think). On the tire issue, we don't yet know if that was the left or the right tire. Plus high heat could have easily increased tire pressure enough as to blow the tire inside the tire well which in turn could have caused more damaged to the hydraulic and other lines that were near by.
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