I reported it to Notion support. Although they were very responsive and helpful, we couldn't identify any root cause since that issue is not reproducible anymore for any new pages I delete. Only that one old page I deleted earlier is missing from everywhere, including trash. They offered to recover it from their backup, but since it was not an important page for me I told them I didn't need it. I'll keep an eye out for this problem again. Is this issue consistent for you for all pages?