Answer
How do I check that a journal is really indexed in Scopus?
Check the Scopus source list at the source rather than trusting a badge on the journal's site. Confirm the title and ISSN match, and look for a coverage end date, which indicates the title was discontinued. Phrases such as 'Scopus approved' or 'under evaluation' mean the journal is not indexed.
Detail
Two further checks worth a minute
Open three articles and confirm the DOIs resolve to the right papers. Look for a written description of the review process rather than the words 'peer reviewed' alone.