This might not be a bug and might work as intended.
Before going further, you will want to read up with this blog post. The most important bits related to your question are these, from the bottom of the blog post:
First, if you’ve contributed something worthwhile to the site, you should keep the reputation for that even if it eventually gets deleted. “Worthwhile” here is defined as,
- A score of 3 or greater
- Visible on the site for at least 60 days
Your questions seems to say that your answer was at least under the first part of that definition.
But, you should first verify that that is indeed the case:
Go to your reputation page
show removed posts box at the bottom.
Verify how you lost your reputation.
The second question is whether your post was on the site for at least two months.
As you are now aware of the recent changes, I'll try to attempt to answer your questions:
Why do the good answerers suffer if a question gets deleted?
I would think that it is very rare that answers would be really good when a question gets deleted, because that is when the question does not adhere to the What kind of questions should I not ask here? FAQ.
If a question is not answerable, chatty, open-ended, wrongly scoped, subjective or meta; then in any of these cases I can't see how it can result in answers that solve a problem or that we can learn from.
Feel free to proof me wrong with an example...
Is the information not pertinent?
Unless personal data needs to be removed or a DMCA complaint has been made, information is still in the system and visible to 10k users and moderators. When people disagree with the deletion of an answer but don't want the question to be open either, the recent changes allow moderators to historically lock the post. This is covered in the above blog post, to keep information pertinent when necessary...