I've never had a marine experience like that so I can only fall back on my structural engineering background. There are a LOT of ways that there could be hidden damage that only surfaces after some hard sailing.
All of the bulkheads and the hull to deck joint are joined by fiberglass. These joints are not exposed to careful inspection and are the place where you could have damage. If one or more of these bulkhead/deck to hull joints are damaged but not to the point where there is visible movement, the joint is nonetheless damaged and does not have the same strength or resistance to fatigue it originally had. The keel is joined to the keel stub by keel bolts. The keel stub and the hull structure it's attached to took a very heavy hit as the 16 tons of boat landed on it. How careful, complete and thorough were the inspection and repairs? After some hard sailing or years of sailing the now over-stressed joints or structure can fail, or result in excessive movement or leaks.
Did they remove everything in the vicinity of the impact (all furniture, cabinets, wall coverings, flooring, etc.) to permit a careful inspection and/or reinforcement? If so perhaps you might feel you're covered if the people doing the work can be trusted or someone you hired was there inspecting. Keep in mind it's always easier and cheaper to cover up than to expose and repair, especially if you plan to sell the boat.
Is there a good chance all is well, sure...maybe. Personally I would not take the chance unless the level of risk (as you view it) is seriously reflected in the sales price and you are willing to take on the risk with eyes wide open. Maybe if you plan on only coastal sailing?