robots.txt closes the road, not the catalogue: to delist, let the bot in and say noindex.

A disallow rule only stops well-behaved bots from fetching a URL. Other sites can still link to it, so it can sit in the index as a bare address with no snippet. To keep a page out of results, leave it fetchable and add a noindex directive. If you block the fetch, the bot never reads that directive.

Read it once, then a question tests whether the trick stuck.