What Do You Do When a Website Doesn't Have a Sitemap?

I was doing a competitor audit recently and ran into something surprisingly common: websites with no obvious sitemap.

No sitemap in robots.txt, no standard /sitemap.xml, and no mention of one anywhere in the source code.

For small sites it's not a huge deal, but when you're auditing dozens of domains, manually hunting for sitemaps becomes a time sink.

I've noticed a few different scenarios:

Sites that forgot to generate a sitemap
CMS installations with non-standard sitemap URLs
Dynamically generated sitemaps
Sites that intentionally hide them
Large websites with multiple sitemap indexes

I'm curious how everyone handles this.

When you can't find a sitemap immediately, what's your process?

Check robots.txt first?
Crawl the site yourself?
Use search operators?
Look for CMS-specific patterns?

Would love to hear the approaches other SEOs and indie hackers use when a sitemap isn't easy to find.