Indexed Answer Box Result Leads to a 404 page?

[HSawhney]

Hey everyone,

One of my clients is currently getting an answer box (people also ask) result for a page that is no longer live. They migrated their site approximately 6 months ago, and the old page is for some reason still indexed in the (people also asked) results. Weird thing is that this page leads to a 404 error.

1. Why the heck is Google showing this?
2. Are there separate indexes for "people also asked" results, and regular organic listings?
3. Has anyone ever seen/experienced something like this before?

Any insight would is much appreciated

[EGOL]

Google does not update these features very often.  We moved some content to another website in February and some of these features are still showing in the SERPs for the old location.

However, we placed 301 redirects on the original pages so that this traffic from Google, existing links from other websites, bookmarks from past customers and many other types of traffic will be redirected to the new destination.

We always put up 301 redirects anytime we move anything and they will be there forever - even after my funeral - and my business continuity plan instructs my heirs to keep these 301s in place.  I believe that holding these 301s in place beyond my lifetime is best practice (I am a lot older than most Moz fans).