Unsupported get request when requesting post by ID while requesting it's comments by ID works

We encounter an issue when it comes to requesting a specific post. It's about an ads-post.
When trying to fetch it by using the page-access token it is not delivered via feed or ads_posts endpoint (while those endpoints return other posts) and when requesting it by ID, the API returns
"Unsupported get request. Object with ID '92204367377_756443629857480' does not exist, cannot be loaded due to missing permissions, or does not support this operation. Please read the Graph API documentation at https://developers.facebook.com/docs/graph-api"
I only got the post ID by a webhook about a comment added to this post. And also interesting: i can successfully request the comment.
Did anyone else encounter such a problem and can provide a solution for it?
Best regards
Martin